Introduction

Immune thrombocytopenia (ITP) is a common acquired autoimmune disease characterized by low platelet counts and an increased risk of bleeding. The incidence of ITP is approximately 3.3 per 100,000 adults.¹ There is considerable controversy about all aspects of the disease, with little “hard” data on which to base decisions given the lack of randomized clinical trials to address most clinical questions. This article reviews the presentation and diagnosis of ITP and its treatment options and discusses management of ITP in specific clinical situations.

Pathogenesis and Epidemiology

ITP is caused by autoantibodies binding to platelet surface proteins, most often to the platelet receptor GP IIb/IIIa.^2-4 These antibody-coated platelets then bind to Fc receptors in macrophages and are removed from circulation. The initiating event in ITP is unknown. It is speculated that the patient responds to a viral or bacterial infection by creating antibodies which cross-react with the platelet receptors. Continued exposure to platelets perpetuates the immune response. ITP that occurs in childhood appears to be an acute response to viral infection and usually resolves. ITP in adults may occur in any age group but is seen especially in young women.

Despite the increased platelet destruction that occurs in ITP, the production of new platelets often is not significantly increased. This is most likely due to lack of an increase in thrombopoietin, the predominant platelet growth factor.⁵

It had been thought that most adult patients who present with ITP go on to have a chronic course, but more recent studies have shown this is not the case. In modern series the percentage of patients who are “cured” with steroids ranges from 30% to 70%.^6–9 In addition, it has been appreciated that even in patients with modest thrombocytopenia, no therapy is required if the platelet count remains higher than 30 × 10³/µL. However, this leaves a considerable number of patients who will require chronic therapy.

Clinical Presentation

Presentation can range from a symptomatic patient with low platelets found on a routine blood count to a patient with massive bleeding. Typically, patients first present with petechiae (small bruises 1 mm in size) on the shins. True petechiae are seen only in severe thrombocytopenia. Patients will also report frequent bruising and bleeding from the gums. Patients with very low platelet counts will notice “wet purpura,” which is characterized by blood-filled bullae in the oral cavity. Life-threatening bleeding is a very unusual presenting sign unless other problems (trauma, ulcers) are present. The physical examination is only remarkable for stigmata of bleeding such as the petechiae. The presence of splenomegaly or lymphadenopathy weighs strongly against a diagnosis of ITP. Many patients with ITP will note fatigue when their platelets counts are lower.¹⁰

Diagnosis

Extremely low platelet counts with a normal blood smear and an otherwise healthy patient are diagnostic of ITP. The platelet count cutoff for considering ITP is 100 × 10³/µL as the majority of patients with counts in the 100 to 150 × 10³/µL range will not develop greater thrombocytopenia.¹¹ Also, the platelet count decreases with age (9 × 10³/µL per decade in one study), and this also needs to be factored into the evaluation.¹² The finding of relatives with ITP should raise suspicion for congenital thrombocytopenia.¹³ One should question the patient carefully about drug exposure (see Drug-Induced Thrombocytopenia), especially about over-the-counter medicines, “natural” remedies, or recreational drugs.

There is no laboratory test that rules in ITP; rather, it is a diagnosis of exclusion. The blood smear should be carefully examined for evidence of microangiopathic hemolytic anemias (schistocytes), bone marrow disease (blasts, teardrop cells), or any other evidence of a primary bone marrow disease. In ITP, the platelets can be larger than normal, but finding some platelets the size of red cells should raise the issue of congenital thrombocytopenia.¹⁴ Pseudo-thrombocytopenia, which is the clumping of platelets due to a reaction to the EDTA anticoagulant in the tube, should be excluded. The diagnosis is established by drawing the blood in a citrated (blue-top) tube to perform the platelet count. There is no role for antiplatelet antibody assay because this test lacks sensitivity and specificity. In a patient without a history of autoimmune disease or symptoms, empiric testing for autoimmune disease is not recommended.

Patients who present with ITP should be tested for both HIV and hepatitis C infection.^15,16 These are the most common viral causes of secondary ITP, and both have prognostic and treatment implications. Some authorities also recommend checking thyroid function as hypothyroidism can present or aggravate the thrombocytopenia.

The role of bone marrow examination is controversial.¹⁷ Patients with a classic presentation of ITP (young woman, normal blood smear) do not require a bone marrow exam before therapy is initiated, although patients who do not respond to initial therapy should have a bone marrow aspiration. The rare entity amegakaryocytic thrombocytopenia can present with a clinical picture similar to that of ITP, but amegakaryocytic thrombocytopenia will not respond to steroids. Bone marrow aspiration reveals the absence of megakaryocytes in this entity. It is rare, however, that another hematologic disease is diagnosed in patients with a classic clinical presentation of ITP.

In the future, measurement of thrombopoietin and reticulated platelets may provide clues to the diagnosis.⁴ Patients with ITP paradoxically have normal or only mildly elevated thrombopoietin levels. The finding of a significantly elevated thrombopoietin level should lead to questioning of the diagnosis. One can also measure “reticulated platelets,” which are analogous to red cell reticulocytes. Patients with ITP (or any platelet destructive disorders) will have high levels of reticulated platelets. These tests are not recommended for routine evaluation, but may be helpful in difficult cases.

Treatment

In general, therapy in ITP should be guided by the patient’s signs of bleeding and not by unquestioning adherence to measuring platelet levels,¹⁵ as patients tolerate thrombocytopenia well. It is unusual to have life-threatening bleeding with platelet counts greater than 5 × 10³/µL in the absence of mechanical lesions. Despite the low platelet count in patients with ITP, the overall mortality is estimated to be only 0.3% to 1.3%.¹⁸ It is sobering that in one study the rate of death from infections was twice as high as that from bleeding.¹⁹ Rare patients will have antibodies that interfere with the function of the platelet, and these patients can have profound bleeding with only modestly lowered platelet counts.²⁰ A suggested cut-off for treating newly diagnosed patients is 30 × 10³/µL.²¹

Initial Therapy

The primary therapy of ITP is glucocorticoids, either prednisone or dexamethasone. In the past prednisone at a dose of 60 to 80 mg/day was started at the time of diagnosis (Table 1).

For rapid induction of a response, there are 2 options. A single dose of intravenous immune globulin (IVIG) at 1 g/kg or intravenous anti-D immunoglobulin (anti-D) at 50 to 75 µg/kg can induce a response in more than 80% of patients in 24 to 48 hours.^21,24 IVIG has several drawbacks. It can cause aseptic meningitis, and in patients with vascular disease the increased viscosity can induce ischemia. There is also a considerable fluid load delivered with the IVIG, and it needs to be given over several hours.

The use of anti-D is limited to Rh-positive patients who have not had a splenectomy. It should not be used in patients who are Coombs positive due to the risk of provoking more hemolysis. Rarely anti-D has been reported to cause a severe hemolytic disseminated intravascular coagulation syndrome (1:20,000 patients), which has led to restrictions in its use.²⁵ Although the drug can be rapidly given over 15 minutes, due to these concerns current recommendations are now to observe patients for 8 hours after their dose and to perform a urine dipstick test for blood at 2, 4, and 8 hours. Concerns about this rare but serious side effect have led to a dramatic decrease in the use of anti-D.

For patients who are severely thrombocytopenic and do not respond to initial therapy, there are 2 options for raising the platelet counts. One is to use a combination of IVIG, methylprednisolone, vincristine, and/or anti-D.²⁶ The combination of IVIG and anti-D may be synergistic since these agents block different Fc receptors. A response of 71% has been reported for this 3- or 4-drug combination in a series of 35 patients.²⁶ The other option is to treat with a continuous infusion of platelets (1 unit over 6 hours) and IVIG 1 g/kg for 24 hours. Response rates of 62.7% have been reported with this combination, and this rapid rise in platelets can allow time for other therapies to take effect.^27,28

Patients with severe thrombocytopenia who relapse with reduction of steroids or who do not respond to steroids have several options for further management. Repeated doses of IVIG can transiently raise the platelet count, and some patients may only need several courses of therapy over the course of many months. One study showed that 60% of patients could delay or defer therapy by receiving multiple doses of anti-D. However, 30% of patients did eventually receive splenectomy and 20% of patients required ongoing therapy with anti-D.²⁹ In a randomized trial comparing early use of anti-D to steroids to avoid splenectomy, there was no difference in splenectomy rate (38% versus 42%).³⁰ Finally, an option as mentioned above is to try a 6-month course of pulse dexamethasone 40 mg/day for 4 days, repeated every 28 days.

Options for Refractory ITP

There are multiple options for patients who do not respond to initial ITP therapies. These can be divided into several broad groups: curative therapies (splenectomy and rituximab), thrombopoietin receptor agonists, and anecdotal therapies.

Splenectomy

In patients with severe thrombocytopenia who do not respond or who relapse with lower doses of prednisone, splenectomy should be strongly considered. Splenectomy will induce a good response in 60% to 70% of patients and is durable in most patients. In 2 recently published reviews of splenectomy, the complete response rate was 67% and the total response rate was 88% to 90%%.^8,31 Between 15% and 28% of patients relapsed over 5 years, with most recurrences occurring in the first 2 years. Splenectomy carries a short-term surgical risk, and the life-long risk of increased susceptibility to overwhelming sepsis is discussed below. However, the absolute magnitude of these risks is low and is often lower than the risks of continued prednisone therapy or of continued cytotoxic therapy.

Timing of splenectomy depends on the patient’s presentation. Most patients should be given a 6-month trial of steroids or other therapies before proceeding to splenectomy.³¹ However, patients who persist with severe thrombocytopenia despite initial therapies or who are suffering intolerable side effects from therapy should be considered sooner for splenectomy.³¹ In the George review, multiple factors such as responding to IVIG were found not to be predictive of response to splenectomy.⁸

Method of splenectomy appears not to matter.²¹ Rates of finding accessory spleens are just as high or higher with laparoscopic splenectomy and the patient can recover faster. In patients who are severely thrombocytopenic, open splenectomy can allow for quicker control of the vascular access of the spleen.

Rates of splenectomy in recent years have decreased for many reasons,³² including the acceptance of lower platelet counts in asymptomatic patients and the availability of alternative therapies such as rituximab. In addition, despite abundant data for good outcomes, there is a concern that splenectomy responses are not durable. Although splenectomy will not cure every patient with ITP, splenectomy is the therapy with the most patients, the longest follow-up, and the most consistent rate of cure, and it should be discussed with every ITP patient who does not respond to initial therapy and needs further treatment.

The risk of overwhelming sepsis varies by indications for splenectomy but appears to be about 1%.^33,34 The use of pneumococcal vaccine and recognition of this syndrome have helped reduce the risk. Asplenic patients need to be counseled about the risk of overwhelming infections, should be vaccinated for pneumococcus, meningococcus, and Haemophilus influenzae, and should wear an ID bracelet.^35–37 Patients previously vaccinated for pneumococcus should be re-vaccinated every 3 to 5 years. The role of prophylactic antibiotics in adults is controversial, but patients under the age of 18 should be on penicillin VK 250 mg orally twice daily.

Rituximab

Rituximab has been shown to be very active in ITP. Most studies used the standard dose of 375 mg/m² weekly for 4 weeks, but other studies have shown that 1000 mg twice 14 days apart (ie, on days 1 and 15) resulted in the same response rate and may be more convenient for patients.^38,39 The response time can vary, with patients either showing a rapid response or requiring up to 8 weeks for their counts to go up. Although experience is limited, the response seems to be durable, especially in those patients whose counts rise higher than 150 × 10³/µL; in patients who relapse, a response can be re-induced with a repeat course. Overall the response rate for rituximab is about 60%, but only approximately 20% to 40% of patients will remain in long-term remission.^40–42 There is no evidence yet that “maintenance” therapy or monitoring CD19/CD20 cells can help further the duration of remission.

Whether to give rituximab pre- or post-splenectomy is also uncertain. An advantage of presplenectomy rituximab is that many patients will achieve remission, delaying the need for surgery. Also, rituximab is a good option for patients whose medical conditions put them at high risk for complications with splenectomy. However, it is unknown whether rituximab poses any long-term risks, while the long-term risks of splenectomy are well-defined. Rituximab is the only curative option left for patients who have failed splenectomy and is a reasonable option for these patients.

There is an intriguing trial in which patients were randomly assigned to dexamethasone alone versus dexamethasone plus rituximab upon presentation with ITP; those who were refractory to dexamethasone alone received salvage therapy with dexamethasone plus rituximab.⁴³ The dexamethasone plus rituximab group had an overall higher rate of sustained remission at 6 months than the dexamethasone group, 63% versus 36%. Interestingly, patients who failed their first course of dexamethasone but then were “salvaged” with dexamethasone/rituximab had a similar overall response rate of 56%, suggesting that saving the addition of rituximab for steroid failures may be an effective option.

Although not “chemotherapy,” rituximab is not without risks. Patients can develop infusion reactions, which can be severe in 1% to 2% of patients. In a meta-analysis the fatal reaction rate was 2.9%.⁴⁰ Patients with chronic hepatitis B infections can experience reactivation with rituximab, and thus all patients should be screened before treatment. Finally, the very rare but devastating complication of progressive multifocal leukoencephalopathy has been reported.

Thrombopoietin Receptor Agonists

Although patients with ITP have low platelet counts, studies starting with Dameshek have shown that these patients also have reduced production of platelets.⁴⁴ Despite the very low circulating platelet count, levels of the platelet growth factor thrombopoietin (TPO) are not raised.⁴⁵ Seminal studies with recombinant TPO in the 1990s showed that ITP patients responded to thrombopoietin-stimulating protein, but the formation of anti-TPO antibodies halted trials with the first generation of these agents. Two TPO receptor agonists (TPO-RA) are approved for use in patients with ITP.

Romiplostim. Romiplostim is a peptibody, a combination of a peptide that binds and stimulates the TPO receptor and an Fc domain to extend its half-life.⁴⁶ It is administered in a weekly subcutaneous dose starting at 1 to 3 µg/kg. Use of romiplostim in ITP patients produces a response rate of 80% to 88%, with 87% of patients being able to wean off or decrease other anti-ITP medications.⁴⁷ In a long-term extension study, the response was again high at 87%.⁴⁸ These studies have also shown a reduced incidence of bleeding.

The major side effect of romiplostim seen in clinical trials was marrow reticulin formation, which occurred in up to 5.6% of patients.^47,48 The clinical course in these patients is the development of anemia and a myelophthisic blood smear with teardrop cells and nucleated red cells. These changes appear to reverse with cessation of the drug. The bone marrow shows increased reticulin formation but rarely, if ever, shows the collagen deposition seen with primary myelofibrosis.

Thrombosis has also been seen, with a rate of 0.08 to 0.1 cases per 100 patient-weeks,⁴⁹ but it remains unclear if this is due to the drug, part of the natural history of ITP, or expected complications in older patients undergoing any type of medical therapy. Surprisingly, despite the low platelet counts, patients with ITP in one study had double the risk of venous thrombosis, demonstrating that ITP itself can be a risk factor for thrombosis.⁵⁰ These trials have shown no long-term concerns for other clinical problems such as liver disease.

Eltrombopag. The other available TPO-RA is eltrombopag,⁵¹ an oral agent that stimulates the TPO receptor by binding the transmembrane domain and activating it. The drug is given orally starting at 50 mg/day (25 mg for patients of Asian ancestry or with liver disease) and can be dose escalated to 75 mg/day. The drug needs to be taken on an empty stomach. Eltrombopag has been shown to be effective in chronic ITP, with response rates of 59% to 80% and reduction in use of rescue medications.^47,51,52 As with romiplostim, the incidence of bleeding was also decreased with eltrombopag in these trials.^47,51

Clinical trials demonstrated that eltrombopag shares with romiplostim the risk for marrow fibrosis. A side effect unique to eltrombopag observed in these trials was a 3% to 7% incidence of elevated liver function tests.^21,52 These abnormal findings appeared to resolve in most patients, but liver function tests need to be monitored in patients receiving eltrombopag.

Clinical use. The clearest indication for the use of TPO-RAs is in patients who have failed several therapies and remain symptomatic or are on intolerable doses of other medications such as prednisone. The clear benefits are their relative safety and high rates of success. The main drawback of TPO-RAs is the need for continuing therapy as the platelet count will return to baseline shortly after these agents are stopped. Currently there is no clear indication for one medication over the other. The advantages of romiplostim are great flexibility in dosing (1–10 µg/kg week) and no concerns about drug interaction. The current drawback of romiplostim is the Food and Drug Administration’s requirement for patients to receive the drug from a clinic and not at home. Eltrombopag offers the advantage of oral use, but it has a limited dose range and potential for drug interactions. Both agents have been associated with marrow reticulin formation, although in clinical use this risk appears to be very low.⁵³

Other Options

In the literature there are numerous options for the treatment of ITP.^54,55 Most of these studies are anecdotal, enrolled small number of patients, and sometimes included patients with mild thrombocytopenia, but these therapeutic options can be tried in patients who are refractory to standard therapies and have bleeding. The agents with the greatest amount of supporting data are danazol, vincristine, azathioprine, cyclophosphamide, and fostamatinib.

Danazol 200 mg 4 times daily is thought to downregulate the macrophage Fc receptor. The onset of action may be delayed and a therapeutic trial of up to 4 to 6 months is advised. Danazol is very effective in patients with antiphospholipid antibody syndrome who develop ITP and may be more effective in premenopausal women.⁵⁶ Once a response is seen, danazol should be continued for 6 months and then an attempt to wean the patient off the agent should be made. A partial response can be seen in 70% to 90% of patients, but a complete response is rare.⁵⁴

Vincristine 1.4 mg/m² weekly has a low response rate, but if a response is going to occur, it will occur rapidly within 2 weeks. Thus, a prolonged trial of vincristine is not needed; if no platelet rise is seen in several weeks, the drug should be stopped. Again, partial responses are more common than complete response—50% to 63% versus 0% to 6%.⁵⁴Azathioprine 150 mg orally daily, like danazol, demonstrates a delayed response and requires several months to assess for response. However, 19% to 25% of patients may have a complete response.⁵⁴ It has been reported that the related agent mycophenolate 1000 mg twice daily is also effective in ITP.⁵⁷

Cyclophosphamide 1 g/m² intravenously repeated every 28 days has been reported to have a response rate of up to 40%.⁵⁸ Although considered more aggressive, this is a standard immunosuppressive dose and should be considered in patients with very low platelet counts. Patients who have not responded to single-agent cyclophosphamide may respond to multi-agent chemotherapy with agents such as etoposide and vincristine plus cyclophosphamide.⁵⁹

Fostamatinib, a spleen tyrosine kinase (SYK) inhibitor, is currently under investigation for the treatment of ITP.⁶⁰ This agent prevents phagocytosis of antibody-coated platelets by macrophages. In early studies fostamatinib has been well tolerated at a dose of 150 mg twice daily, with 75% of patients showing a response. Large phase 3 trials are underway, and if the earlier promising results hold up fostamatinib may be a novel option for refractory patients.

A Practical Approach to Refractory ITP

One approach is to divide patients into bleeders, or those with either very low platelet counts (< 5 × 10³/µL) or who have had significant bleeding in the past, and nonbleeders, or those with platelet counts above 5 × 10³/µL and no history of severe bleeding. Bleeders who do not respond adequately to splenectomy should first start with rituximab since it is not cytotoxic and is the only other “curative” therapy (Table 2).

Nonbleeders should be tried on danazol and other relatively safe agents. If this fails, rituximab or TPO-RAs can be considered. Before one considers cytotoxic therapy, the risk of the therapy must be weighed against the risk posed by the thrombocytopenia. The mortality from ITP is fairly low (5%) and is restricted to patients with severe disease. Patients with only moderate thrombocytopenia and no bleeding are better served with conservative management. There is little justification for the use of continuous steroid therapy in this group of patients given the long-term risks of this therapy.

Special Situations

Surgery

Patients with ITP who need surgery either for splenectomy or for other reasons should have their platelet counts raised to a level greater than 20 to 30 × 10³/µL before surgery. Most patients with ITP have increased platelet function and will not have excessive bleeding with these platelet counts. For patients with platelet counts below this level, an infusion of immune globulin or anti-D may rapidly increase the platelet counts. If the surgery is elective, short-term use of TPO-RAs to raise the counts can also be considered.

Pregnancy

Up to 10% of pregnant women will develop low platelet counts during their pregnancy.^61,62 The most common etiology is gestational thrombocytopenia, which is an exaggeration of the lowered platelet count seen in pregnancy. Counts may fall as low as 50 × 10³/µL at the time of delivery. No therapy is required as the fetus is not affected and the mother does not have an increased risk of bleeding. Pregnancy complications such as HELLP syndrome and thrombotic microangiopathies also present with low platelet counts, but these can be diagnosed by history.^61,63

Women with ITP can either develop the disease during pregnancy or have a worsening of the symptoms.⁶⁴ Counts often drop dramatically during the first trimester. Early management should be conservative with low doses of prednisone to keep the count above 10 × 10³/µL.²¹ Immunoglobulin is also effective,⁶⁵ but there are rare reports of pulmonary edema. Rarely patients who are refractory will require splenectomy, which may be safely performed in the second trimester. For delivery the count should be greater than 30 × 10³/µL and for an epidural greater than 50 × 10³/µL.⁶⁴ There are reports of the use of TPO-RAs in pregnancy, and this can be considered for refractory cases.⁶⁶

Most controversy centers on management of the delivery. In the past it was feared that fetal thrombocytopenia could lead to intracranial hemorrhage, and Caesarean section was always recommended. It now appears that most cases of intracranial hemorrhage were due to alloimmune thrombocytopenia and not ITP. Furthermore, the nadir of the baby’s platelet count is not at birth but several days after. It appears the safest course is to proceed with a vaginal or C-section delivery determined by obstetrical indications and then immediately check the baby’s platelet count. If the platelet count is low in the neonate, immunoglobulin will raise the count. Since the neonatal thrombocytopenia is due to passive transfer of maternal antibody, the platelet destruction will abate in 4 to 6 weeks.

Pediatric Patients

The incidence of ITP in children is 2.2 to 5.3 per 100,000 children.¹ There are several distinct differences in pediatric ITP. Most cases will resolve in weeks, with only a minority of patients transforming into chronic ITP (5%–10%). Also, the rates of serious bleeding are lower in children than in adults, with intracranial hemorrhage rates of 0.1% to 0.5% being seen.⁶⁷ For most patients with no or mild bleeding, management now is observation alone regardless of platelet count because it is felt that the risks of therapies are higher than the risk of bleeding.²¹ For patients with bleeding, IVIG, anti-D, or a short course of steroids can be used. Given the risk of overwhelming sepsis, splenectomy is often deferred as long as possible. Rituximab is increasingly being used in children due to concerns about use of agents such a cyclophosphamide or azathioprine in children.⁶⁸ Abundant data on use of TPO-RAs in children showing high response rates and safety support their use, and these should be considered in refractory ITP before any cytotoxic agent.^69–71

Helicobacter Pylori Infection

There has been much interest in the relationship between H. pylori and ITP.^16,72,73H. pylori infections have been associated with a variety of autoimmune diseases, and there is a confusing literature on this infection and ITP. Several meta-analyses have shown that eradication of H. pylori will result in an ITP response rate of 20% to 30%, but responses curiously appear to be limited to certain geographic areas such as Japan and Italy but not the United States. In patients with recalcitrant ITP, especially in geographic areas with high incidence, it may be worthwhile to check for H. pylori infection and treat accordingly if positive.

Drug-Induced Thrombocytopenia

Patients with drug-induced thrombocytopenia present with very low (< 10 × 10³/µL) platelet counts 1 to 3 weeks after starting a new medication.^74–76 In patients with a possible drug-induced thrombocytopenia, the primary therapy is to stop the suspect drug.⁷⁷ If there are multiple new medications, the best approach is to stop any drug that has been strongly associated with thrombocytopenia (Table 3).^74,78,79

Immune globulin, corticosteroids, or intravenous anti‑D have been suggested as useful in drug‑related thrombocytopenia. However, since most of these thrombocytopenic patients recover when the agent is cleared from the body, this therapy is probably not necessary and withholding treatment avoids exposing the patients to the adverse events associated with further therapy.

Evans Syndrome

Evans syndrome is defined as the combination of autoimmune hemolytic anemia (AIHA) and ITP.^80,81 These cytopenias can present simultaneously or sequentially. Patients with Evans syndrome are thought to have a more severe disease process, to be more prone to bleeding, and to be more difficult to treat, but the rarity of this syndrome makes this hard to quantify.

The classic clinical presentation of Evans syndrome is severe anemia and thrombocytopenia. Children with Evans syndrome often have complex immunodeficiencies such as autoimmune lymphoproliferative syndrome.^82,83 In adults, Evans syndrome most often complicates other autoimmune diseases such as lupus. There are increasing reports of Evans syndrome occurring as a complication of T-cell lymphomas. Often the autoimmune disease can predate the lymphoma diagnosis by months or even years.

In theory the diagnostic approach is straightforward by showing a Coombs-positive hemolytic anemia in the setting of a clinical diagnosis of immune thrombocytopenia. The blood smear will show spherocytes and a diminished platelet count. The presence of other abnormal red cell forms should raise the possibility of an alternative diagnosis. It is unclear how vigorously one should search for other underlying diseases. Many patients will already have the diagnosis of an underlying autoimmune disease. The presence of lymphadenopathy should raise concern for lymphoma.

Initial therapy is high-dose steroids (2 mg/kg/day). IVIG should be added if severe thrombocytopenia is present. Patients who cannot be weaned off prednisone or relapse after prednisone should be considered for splenectomy, although these patients are at higher risk of relapsing.⁸⁰ Increasingly rituximab is being used with success.^84,85 For patients who fail splenectomy and rituximab, aggressive immunosuppression should be considered. Increasing data support the benefits of sirolimus, and this should be considered for refractory patients.⁸⁶ For patients with Evans syndrome due to underlying lymphoma, antineoplastic therapy often results in prompt resolution of the symptoms. Recurrence of the autoimmune cytopenias often heralds relapse.

Introduction

Immune thrombocytopenia (ITP) is a common acquired autoimmune disease characterized by low platelet counts and an increased risk of bleeding. The incidence of ITP is approximately 3.3 per 100,000 adults.¹ There is considerable controversy about all aspects of the disease, with little “hard” data on which to base decisions given the lack of randomized clinical trials to address most clinical questions. This article reviews the presentation and diagnosis of ITP and its treatment options and discusses management of ITP in specific clinical situations.

Pathogenesis and Epidemiology

ITP is caused by autoantibodies binding to platelet surface proteins, most often to the platelet receptor GP IIb/IIIa.^2-4 These antibody-coated platelets then bind to Fc receptors in macrophages and are removed from circulation. The initiating event in ITP is unknown. It is speculated that the patient responds to a viral or bacterial infection by creating antibodies which cross-react with the platelet receptors. Continued exposure to platelets perpetuates the immune response. ITP that occurs in childhood appears to be an acute response to viral infection and usually resolves. ITP in adults may occur in any age group but is seen especially in young women.

Despite the increased platelet destruction that occurs in ITP, the production of new platelets often is not significantly increased. This is most likely due to lack of an increase in thrombopoietin, the predominant platelet growth factor.⁵

It had been thought that most adult patients who present with ITP go on to have a chronic course, but more recent studies have shown this is not the case. In modern series the percentage of patients who are “cured” with steroids ranges from 30% to 70%.^6–9 In addition, it has been appreciated that even in patients with modest thrombocytopenia, no therapy is required if the platelet count remains higher than 30 × 10³/µL. However, this leaves a considerable number of patients who will require chronic therapy.

Clinical Presentation

Presentation can range from a symptomatic patient with low platelets found on a routine blood count to a patient with massive bleeding. Typically, patients first present with petechiae (small bruises 1 mm in size) on the shins. True petechiae are seen only in severe thrombocytopenia. Patients will also report frequent bruising and bleeding from the gums. Patients with very low platelet counts will notice “wet purpura,” which is characterized by blood-filled bullae in the oral cavity. Life-threatening bleeding is a very unusual presenting sign unless other problems (trauma, ulcers) are present. The physical examination is only remarkable for stigmata of bleeding such as the petechiae. The presence of splenomegaly or lymphadenopathy weighs strongly against a diagnosis of ITP. Many patients with ITP will note fatigue when their platelets counts are lower.¹⁰

Diagnosis

Extremely low platelet counts with a normal blood smear and an otherwise healthy patient are diagnostic of ITP. The platelet count cutoff for considering ITP is 100 × 10³/µL as the majority of patients with counts in the 100 to 150 × 10³/µL range will not develop greater thrombocytopenia.¹¹ Also, the platelet count decreases with age (9 × 10³/µL per decade in one study), and this also needs to be factored into the evaluation.¹² The finding of relatives with ITP should raise suspicion for congenital thrombocytopenia.¹³ One should question the patient carefully about drug exposure (see Drug-Induced Thrombocytopenia), especially about over-the-counter medicines, “natural” remedies, or recreational drugs.

There is no laboratory test that rules in ITP; rather, it is a diagnosis of exclusion. The blood smear should be carefully examined for evidence of microangiopathic hemolytic anemias (schistocytes), bone marrow disease (blasts, teardrop cells), or any other evidence of a primary bone marrow disease. In ITP, the platelets can be larger than normal, but finding some platelets the size of red cells should raise the issue of congenital thrombocytopenia.¹⁴ Pseudo-thrombocytopenia, which is the clumping of platelets due to a reaction to the EDTA anticoagulant in the tube, should be excluded. The diagnosis is established by drawing the blood in a citrated (blue-top) tube to perform the platelet count. There is no role for antiplatelet antibody assay because this test lacks sensitivity and specificity. In a patient without a history of autoimmune disease or symptoms, empiric testing for autoimmune disease is not recommended.

Patients who present with ITP should be tested for both HIV and hepatitis C infection.^15,16 These are the most common viral causes of secondary ITP, and both have prognostic and treatment implications. Some authorities also recommend checking thyroid function as hypothyroidism can present or aggravate the thrombocytopenia.

The role of bone marrow examination is controversial.¹⁷ Patients with a classic presentation of ITP (young woman, normal blood smear) do not require a bone marrow exam before therapy is initiated, although patients who do not respond to initial therapy should have a bone marrow aspiration. The rare entity amegakaryocytic thrombocytopenia can present with a clinical picture similar to that of ITP, but amegakaryocytic thrombocytopenia will not respond to steroids. Bone marrow aspiration reveals the absence of megakaryocytes in this entity. It is rare, however, that another hematologic disease is diagnosed in patients with a classic clinical presentation of ITP.

In the future, measurement of thrombopoietin and reticulated platelets may provide clues to the diagnosis.⁴ Patients with ITP paradoxically have normal or only mildly elevated thrombopoietin levels. The finding of a significantly elevated thrombopoietin level should lead to questioning of the diagnosis. One can also measure “reticulated platelets,” which are analogous to red cell reticulocytes. Patients with ITP (or any platelet destructive disorders) will have high levels of reticulated platelets. These tests are not recommended for routine evaluation, but may be helpful in difficult cases.

Treatment

In general, therapy in ITP should be guided by the patient’s signs of bleeding and not by unquestioning adherence to measuring platelet levels,¹⁵ as patients tolerate thrombocytopenia well. It is unusual to have life-threatening bleeding with platelet counts greater than 5 × 10³/µL in the absence of mechanical lesions. Despite the low platelet count in patients with ITP, the overall mortality is estimated to be only 0.3% to 1.3%.¹⁸ It is sobering that in one study the rate of death from infections was twice as high as that from bleeding.¹⁹ Rare patients will have antibodies that interfere with the function of the platelet, and these patients can have profound bleeding with only modestly lowered platelet counts.²⁰ A suggested cut-off for treating newly diagnosed patients is 30 × 10³/µL.²¹

Initial Therapy

The primary therapy of ITP is glucocorticoids, either prednisone or dexamethasone. In the past prednisone at a dose of 60 to 80 mg/day was started at the time of diagnosis (Table 1).

For rapid induction of a response, there are 2 options. A single dose of intravenous immune globulin (IVIG) at 1 g/kg or intravenous anti-D immunoglobulin (anti-D) at 50 to 75 µg/kg can induce a response in more than 80% of patients in 24 to 48 hours.^21,24 IVIG has several drawbacks. It can cause aseptic meningitis, and in patients with vascular disease the increased viscosity can induce ischemia. There is also a considerable fluid load delivered with the IVIG, and it needs to be given over several hours.

The use of anti-D is limited to Rh-positive patients who have not had a splenectomy. It should not be used in patients who are Coombs positive due to the risk of provoking more hemolysis. Rarely anti-D has been reported to cause a severe hemolytic disseminated intravascular coagulation syndrome (1:20,000 patients), which has led to restrictions in its use.²⁵ Although the drug can be rapidly given over 15 minutes, due to these concerns current recommendations are now to observe patients for 8 hours after their dose and to perform a urine dipstick test for blood at 2, 4, and 8 hours. Concerns about this rare but serious side effect have led to a dramatic decrease in the use of anti-D.

For patients who are severely thrombocytopenic and do not respond to initial therapy, there are 2 options for raising the platelet counts. One is to use a combination of IVIG, methylprednisolone, vincristine, and/or anti-D.²⁶ The combination of IVIG and anti-D may be synergistic since these agents block different Fc receptors. A response of 71% has been reported for this 3- or 4-drug combination in a series of 35 patients.²⁶ The other option is to treat with a continuous infusion of platelets (1 unit over 6 hours) and IVIG 1 g/kg for 24 hours. Response rates of 62.7% have been reported with this combination, and this rapid rise in platelets can allow time for other therapies to take effect.^27,28

Patients with severe thrombocytopenia who relapse with reduction of steroids or who do not respond to steroids have several options for further management. Repeated doses of IVIG can transiently raise the platelet count, and some patients may only need several courses of therapy over the course of many months. One study showed that 60% of patients could delay or defer therapy by receiving multiple doses of anti-D. However, 30% of patients did eventually receive splenectomy and 20% of patients required ongoing therapy with anti-D.²⁹ In a randomized trial comparing early use of anti-D to steroids to avoid splenectomy, there was no difference in splenectomy rate (38% versus 42%).³⁰ Finally, an option as mentioned above is to try a 6-month course of pulse dexamethasone 40 mg/day for 4 days, repeated every 28 days.

Options for Refractory ITP

There are multiple options for patients who do not respond to initial ITP therapies. These can be divided into several broad groups: curative therapies (splenectomy and rituximab), thrombopoietin receptor agonists, and anecdotal therapies.

Splenectomy

In patients with severe thrombocytopenia who do not respond or who relapse with lower doses of prednisone, splenectomy should be strongly considered. Splenectomy will induce a good response in 60% to 70% of patients and is durable in most patients. In 2 recently published reviews of splenectomy, the complete response rate was 67% and the total response rate was 88% to 90%%.^8,31 Between 15% and 28% of patients relapsed over 5 years, with most recurrences occurring in the first 2 years. Splenectomy carries a short-term surgical risk, and the life-long risk of increased susceptibility to overwhelming sepsis is discussed below. However, the absolute magnitude of these risks is low and is often lower than the risks of continued prednisone therapy or of continued cytotoxic therapy.

Timing of splenectomy depends on the patient’s presentation. Most patients should be given a 6-month trial of steroids or other therapies before proceeding to splenectomy.³¹ However, patients who persist with severe thrombocytopenia despite initial therapies or who are suffering intolerable side effects from therapy should be considered sooner for splenectomy.³¹ In the George review, multiple factors such as responding to IVIG were found not to be predictive of response to splenectomy.⁸

Method of splenectomy appears not to matter.²¹ Rates of finding accessory spleens are just as high or higher with laparoscopic splenectomy and the patient can recover faster. In patients who are severely thrombocytopenic, open splenectomy can allow for quicker control of the vascular access of the spleen.

Rates of splenectomy in recent years have decreased for many reasons,³² including the acceptance of lower platelet counts in asymptomatic patients and the availability of alternative therapies such as rituximab. In addition, despite abundant data for good outcomes, there is a concern that splenectomy responses are not durable. Although splenectomy will not cure every patient with ITP, splenectomy is the therapy with the most patients, the longest follow-up, and the most consistent rate of cure, and it should be discussed with every ITP patient who does not respond to initial therapy and needs further treatment.

The risk of overwhelming sepsis varies by indications for splenectomy but appears to be about 1%.^33,34 The use of pneumococcal vaccine and recognition of this syndrome have helped reduce the risk. Asplenic patients need to be counseled about the risk of overwhelming infections, should be vaccinated for pneumococcus, meningococcus, and Haemophilus influenzae, and should wear an ID bracelet.^35–37 Patients previously vaccinated for pneumococcus should be re-vaccinated every 3 to 5 years. The role of prophylactic antibiotics in adults is controversial, but patients under the age of 18 should be on penicillin VK 250 mg orally twice daily.

Rituximab

Rituximab has been shown to be very active in ITP. Most studies used the standard dose of 375 mg/m² weekly for 4 weeks, but other studies have shown that 1000 mg twice 14 days apart (ie, on days 1 and 15) resulted in the same response rate and may be more convenient for patients.^38,39 The response time can vary, with patients either showing a rapid response or requiring up to 8 weeks for their counts to go up. Although experience is limited, the response seems to be durable, especially in those patients whose counts rise higher than 150 × 10³/µL; in patients who relapse, a response can be re-induced with a repeat course. Overall the response rate for rituximab is about 60%, but only approximately 20% to 40% of patients will remain in long-term remission.^40–42 There is no evidence yet that “maintenance” therapy or monitoring CD19/CD20 cells can help further the duration of remission.

Whether to give rituximab pre- or post-splenectomy is also uncertain. An advantage of presplenectomy rituximab is that many patients will achieve remission, delaying the need for surgery. Also, rituximab is a good option for patients whose medical conditions put them at high risk for complications with splenectomy. However, it is unknown whether rituximab poses any long-term risks, while the long-term risks of splenectomy are well-defined. Rituximab is the only curative option left for patients who have failed splenectomy and is a reasonable option for these patients.

There is an intriguing trial in which patients were randomly assigned to dexamethasone alone versus dexamethasone plus rituximab upon presentation with ITP; those who were refractory to dexamethasone alone received salvage therapy with dexamethasone plus rituximab.⁴³ The dexamethasone plus rituximab group had an overall higher rate of sustained remission at 6 months than the dexamethasone group, 63% versus 36%. Interestingly, patients who failed their first course of dexamethasone but then were “salvaged” with dexamethasone/rituximab had a similar overall response rate of 56%, suggesting that saving the addition of rituximab for steroid failures may be an effective option.

Although not “chemotherapy,” rituximab is not without risks. Patients can develop infusion reactions, which can be severe in 1% to 2% of patients. In a meta-analysis the fatal reaction rate was 2.9%.⁴⁰ Patients with chronic hepatitis B infections can experience reactivation with rituximab, and thus all patients should be screened before treatment. Finally, the very rare but devastating complication of progressive multifocal leukoencephalopathy has been reported.

Thrombopoietin Receptor Agonists

Although patients with ITP have low platelet counts, studies starting with Dameshek have shown that these patients also have reduced production of platelets.⁴⁴ Despite the very low circulating platelet count, levels of the platelet growth factor thrombopoietin (TPO) are not raised.⁴⁵ Seminal studies with recombinant TPO in the 1990s showed that ITP patients responded to thrombopoietin-stimulating protein, but the formation of anti-TPO antibodies halted trials with the first generation of these agents. Two TPO receptor agonists (TPO-RA) are approved for use in patients with ITP.

Romiplostim. Romiplostim is a peptibody, a combination of a peptide that binds and stimulates the TPO receptor and an Fc domain to extend its half-life.⁴⁶ It is administered in a weekly subcutaneous dose starting at 1 to 3 µg/kg. Use of romiplostim in ITP patients produces a response rate of 80% to 88%, with 87% of patients being able to wean off or decrease other anti-ITP medications.⁴⁷ In a long-term extension study, the response was again high at 87%.⁴⁸ These studies have also shown a reduced incidence of bleeding.

The major side effect of romiplostim seen in clinical trials was marrow reticulin formation, which occurred in up to 5.6% of patients.^47,48 The clinical course in these patients is the development of anemia and a myelophthisic blood smear with teardrop cells and nucleated red cells. These changes appear to reverse with cessation of the drug. The bone marrow shows increased reticulin formation but rarely, if ever, shows the collagen deposition seen with primary myelofibrosis.

Thrombosis has also been seen, with a rate of 0.08 to 0.1 cases per 100 patient-weeks,⁴⁹ but it remains unclear if this is due to the drug, part of the natural history of ITP, or expected complications in older patients undergoing any type of medical therapy. Surprisingly, despite the low platelet counts, patients with ITP in one study had double the risk of venous thrombosis, demonstrating that ITP itself can be a risk factor for thrombosis.⁵⁰ These trials have shown no long-term concerns for other clinical problems such as liver disease.

Eltrombopag. The other available TPO-RA is eltrombopag,⁵¹ an oral agent that stimulates the TPO receptor by binding the transmembrane domain and activating it. The drug is given orally starting at 50 mg/day (25 mg for patients of Asian ancestry or with liver disease) and can be dose escalated to 75 mg/day. The drug needs to be taken on an empty stomach. Eltrombopag has been shown to be effective in chronic ITP, with response rates of 59% to 80% and reduction in use of rescue medications.^47,51,52 As with romiplostim, the incidence of bleeding was also decreased with eltrombopag in these trials.^47,51

Clinical trials demonstrated that eltrombopag shares with romiplostim the risk for marrow fibrosis. A side effect unique to eltrombopag observed in these trials was a 3% to 7% incidence of elevated liver function tests.^21,52 These abnormal findings appeared to resolve in most patients, but liver function tests need to be monitored in patients receiving eltrombopag.

Clinical use. The clearest indication for the use of TPO-RAs is in patients who have failed several therapies and remain symptomatic or are on intolerable doses of other medications such as prednisone. The clear benefits are their relative safety and high rates of success. The main drawback of TPO-RAs is the need for continuing therapy as the platelet count will return to baseline shortly after these agents are stopped. Currently there is no clear indication for one medication over the other. The advantages of romiplostim are great flexibility in dosing (1–10 µg/kg week) and no concerns about drug interaction. The current drawback of romiplostim is the Food and Drug Administration’s requirement for patients to receive the drug from a clinic and not at home. Eltrombopag offers the advantage of oral use, but it has a limited dose range and potential for drug interactions. Both agents have been associated with marrow reticulin formation, although in clinical use this risk appears to be very low.⁵³

Other Options

In the literature there are numerous options for the treatment of ITP.^54,55 Most of these studies are anecdotal, enrolled small number of patients, and sometimes included patients with mild thrombocytopenia, but these therapeutic options can be tried in patients who are refractory to standard therapies and have bleeding. The agents with the greatest amount of supporting data are danazol, vincristine, azathioprine, cyclophosphamide, and fostamatinib.

Danazol 200 mg 4 times daily is thought to downregulate the macrophage Fc receptor. The onset of action may be delayed and a therapeutic trial of up to 4 to 6 months is advised. Danazol is very effective in patients with antiphospholipid antibody syndrome who develop ITP and may be more effective in premenopausal women.⁵⁶ Once a response is seen, danazol should be continued for 6 months and then an attempt to wean the patient off the agent should be made. A partial response can be seen in 70% to 90% of patients, but a complete response is rare.⁵⁴

Vincristine 1.4 mg/m² weekly has a low response rate, but if a response is going to occur, it will occur rapidly within 2 weeks. Thus, a prolonged trial of vincristine is not needed; if no platelet rise is seen in several weeks, the drug should be stopped. Again, partial responses are more common than complete response—50% to 63% versus 0% to 6%.⁵⁴Azathioprine 150 mg orally daily, like danazol, demonstrates a delayed response and requires several months to assess for response. However, 19% to 25% of patients may have a complete response.⁵⁴ It has been reported that the related agent mycophenolate 1000 mg twice daily is also effective in ITP.⁵⁷

Cyclophosphamide 1 g/m² intravenously repeated every 28 days has been reported to have a response rate of up to 40%.⁵⁸ Although considered more aggressive, this is a standard immunosuppressive dose and should be considered in patients with very low platelet counts. Patients who have not responded to single-agent cyclophosphamide may respond to multi-agent chemotherapy with agents such as etoposide and vincristine plus cyclophosphamide.⁵⁹

Fostamatinib, a spleen tyrosine kinase (SYK) inhibitor, is currently under investigation for the treatment of ITP.⁶⁰ This agent prevents phagocytosis of antibody-coated platelets by macrophages. In early studies fostamatinib has been well tolerated at a dose of 150 mg twice daily, with 75% of patients showing a response. Large phase 3 trials are underway, and if the earlier promising results hold up fostamatinib may be a novel option for refractory patients.

A Practical Approach to Refractory ITP

One approach is to divide patients into bleeders, or those with either very low platelet counts (< 5 × 10³/µL) or who have had significant bleeding in the past, and nonbleeders, or those with platelet counts above 5 × 10³/µL and no history of severe bleeding. Bleeders who do not respond adequately to splenectomy should first start with rituximab since it is not cytotoxic and is the only other “curative” therapy (Table 2).

Nonbleeders should be tried on danazol and other relatively safe agents. If this fails, rituximab or TPO-RAs can be considered. Before one considers cytotoxic therapy, the risk of the therapy must be weighed against the risk posed by the thrombocytopenia. The mortality from ITP is fairly low (5%) and is restricted to patients with severe disease. Patients with only moderate thrombocytopenia and no bleeding are better served with conservative management. There is little justification for the use of continuous steroid therapy in this group of patients given the long-term risks of this therapy.

Special Situations

Surgery

Patients with ITP who need surgery either for splenectomy or for other reasons should have their platelet counts raised to a level greater than 20 to 30 × 10³/µL before surgery. Most patients with ITP have increased platelet function and will not have excessive bleeding with these platelet counts. For patients with platelet counts below this level, an infusion of immune globulin or anti-D may rapidly increase the platelet counts. If the surgery is elective, short-term use of TPO-RAs to raise the counts can also be considered.

Pregnancy

Up to 10% of pregnant women will develop low platelet counts during their pregnancy.^61,62 The most common etiology is gestational thrombocytopenia, which is an exaggeration of the lowered platelet count seen in pregnancy. Counts may fall as low as 50 × 10³/µL at the time of delivery. No therapy is required as the fetus is not affected and the mother does not have an increased risk of bleeding. Pregnancy complications such as HELLP syndrome and thrombotic microangiopathies also present with low platelet counts, but these can be diagnosed by history.^61,63

Women with ITP can either develop the disease during pregnancy or have a worsening of the symptoms.⁶⁴ Counts often drop dramatically during the first trimester. Early management should be conservative with low doses of prednisone to keep the count above 10 × 10³/µL.²¹ Immunoglobulin is also effective,⁶⁵ but there are rare reports of pulmonary edema. Rarely patients who are refractory will require splenectomy, which may be safely performed in the second trimester. For delivery the count should be greater than 30 × 10³/µL and for an epidural greater than 50 × 10³/µL.⁶⁴ There are reports of the use of TPO-RAs in pregnancy, and this can be considered for refractory cases.⁶⁶

Most controversy centers on management of the delivery. In the past it was feared that fetal thrombocytopenia could lead to intracranial hemorrhage, and Caesarean section was always recommended. It now appears that most cases of intracranial hemorrhage were due to alloimmune thrombocytopenia and not ITP. Furthermore, the nadir of the baby’s platelet count is not at birth but several days after. It appears the safest course is to proceed with a vaginal or C-section delivery determined by obstetrical indications and then immediately check the baby’s platelet count. If the platelet count is low in the neonate, immunoglobulin will raise the count. Since the neonatal thrombocytopenia is due to passive transfer of maternal antibody, the platelet destruction will abate in 4 to 6 weeks.

Pediatric Patients

The incidence of ITP in children is 2.2 to 5.3 per 100,000 children.¹ There are several distinct differences in pediatric ITP. Most cases will resolve in weeks, with only a minority of patients transforming into chronic ITP (5%–10%). Also, the rates of serious bleeding are lower in children than in adults, with intracranial hemorrhage rates of 0.1% to 0.5% being seen.⁶⁷ For most patients with no or mild bleeding, management now is observation alone regardless of platelet count because it is felt that the risks of therapies are higher than the risk of bleeding.²¹ For patients with bleeding, IVIG, anti-D, or a short course of steroids can be used. Given the risk of overwhelming sepsis, splenectomy is often deferred as long as possible. Rituximab is increasingly being used in children due to concerns about use of agents such a cyclophosphamide or azathioprine in children.⁶⁸ Abundant data on use of TPO-RAs in children showing high response rates and safety support their use, and these should be considered in refractory ITP before any cytotoxic agent.^69–71

Helicobacter Pylori Infection

There has been much interest in the relationship between H. pylori and ITP.^16,72,73H. pylori infections have been associated with a variety of autoimmune diseases, and there is a confusing literature on this infection and ITP. Several meta-analyses have shown that eradication of H. pylori will result in an ITP response rate of 20% to 30%, but responses curiously appear to be limited to certain geographic areas such as Japan and Italy but not the United States. In patients with recalcitrant ITP, especially in geographic areas with high incidence, it may be worthwhile to check for H. pylori infection and treat accordingly if positive.

Drug-Induced Thrombocytopenia

Patients with drug-induced thrombocytopenia present with very low (< 10 × 10³/µL) platelet counts 1 to 3 weeks after starting a new medication.^74–76 In patients with a possible drug-induced thrombocytopenia, the primary therapy is to stop the suspect drug.⁷⁷ If there are multiple new medications, the best approach is to stop any drug that has been strongly associated with thrombocytopenia (Table 3).^74,78,79

Immune globulin, corticosteroids, or intravenous anti‑D have been suggested as useful in drug‑related thrombocytopenia. However, since most of these thrombocytopenic patients recover when the agent is cleared from the body, this therapy is probably not necessary and withholding treatment avoids exposing the patients to the adverse events associated with further therapy.

Evans Syndrome

Evans syndrome is defined as the combination of autoimmune hemolytic anemia (AIHA) and ITP.^80,81 These cytopenias can present simultaneously or sequentially. Patients with Evans syndrome are thought to have a more severe disease process, to be more prone to bleeding, and to be more difficult to treat, but the rarity of this syndrome makes this hard to quantify.

The classic clinical presentation of Evans syndrome is severe anemia and thrombocytopenia. Children with Evans syndrome often have complex immunodeficiencies such as autoimmune lymphoproliferative syndrome.^82,83 In adults, Evans syndrome most often complicates other autoimmune diseases such as lupus. There are increasing reports of Evans syndrome occurring as a complication of T-cell lymphomas. Often the autoimmune disease can predate the lymphoma diagnosis by months or even years.

In theory the diagnostic approach is straightforward by showing a Coombs-positive hemolytic anemia in the setting of a clinical diagnosis of immune thrombocytopenia. The blood smear will show spherocytes and a diminished platelet count. The presence of other abnormal red cell forms should raise the possibility of an alternative diagnosis. It is unclear how vigorously one should search for other underlying diseases. Many patients will already have the diagnosis of an underlying autoimmune disease. The presence of lymphadenopathy should raise concern for lymphoma.

Initial therapy is high-dose steroids (2 mg/kg/day). IVIG should be added if severe thrombocytopenia is present. Patients who cannot be weaned off prednisone or relapse after prednisone should be considered for splenectomy, although these patients are at higher risk of relapsing.⁸⁰ Increasingly rituximab is being used with success.^84,85 For patients who fail splenectomy and rituximab, aggressive immunosuppression should be considered. Increasing data support the benefits of sirolimus, and this should be considered for refractory patients.⁸⁶ For patients with Evans syndrome due to underlying lymphoma, antineoplastic therapy often results in prompt resolution of the symptoms. Recurrence of the autoimmune cytopenias often heralds relapse.

Introduction

Immune thrombocytopenia (ITP) is a common acquired autoimmune disease characterized by low platelet counts and an increased risk of bleeding. The incidence of ITP is approximately 3.3 per 100,000 adults.¹ There is considerable controversy about all aspects of the disease, with little “hard” data on which to base decisions given the lack of randomized clinical trials to address most clinical questions. This article reviews the presentation and diagnosis of ITP and its treatment options and discusses management of ITP in specific clinical situations.

Pathogenesis and Epidemiology

ITP is caused by autoantibodies binding to platelet surface proteins, most often to the platelet receptor GP IIb/IIIa.^2-4 These antibody-coated platelets then bind to Fc receptors in macrophages and are removed from circulation. The initiating event in ITP is unknown. It is speculated that the patient responds to a viral or bacterial infection by creating antibodies which cross-react with the platelet receptors. Continued exposure to platelets perpetuates the immune response. ITP that occurs in childhood appears to be an acute response to viral infection and usually resolves. ITP in adults may occur in any age group but is seen especially in young women.

Despite the increased platelet destruction that occurs in ITP, the production of new platelets often is not significantly increased. This is most likely due to lack of an increase in thrombopoietin, the predominant platelet growth factor.⁵

It had been thought that most adult patients who present with ITP go on to have a chronic course, but more recent studies have shown this is not the case. In modern series the percentage of patients who are “cured” with steroids ranges from 30% to 70%.^6–9 In addition, it has been appreciated that even in patients with modest thrombocytopenia, no therapy is required if the platelet count remains higher than 30 × 10³/µL. However, this leaves a considerable number of patients who will require chronic therapy.

Clinical Presentation

Presentation can range from a symptomatic patient with low platelets found on a routine blood count to a patient with massive bleeding. Typically, patients first present with petechiae (small bruises 1 mm in size) on the shins. True petechiae are seen only in severe thrombocytopenia. Patients will also report frequent bruising and bleeding from the gums. Patients with very low platelet counts will notice “wet purpura,” which is characterized by blood-filled bullae in the oral cavity. Life-threatening bleeding is a very unusual presenting sign unless other problems (trauma, ulcers) are present. The physical examination is only remarkable for stigmata of bleeding such as the petechiae. The presence of splenomegaly or lymphadenopathy weighs strongly against a diagnosis of ITP. Many patients with ITP will note fatigue when their platelets counts are lower.¹⁰

Diagnosis

Extremely low platelet counts with a normal blood smear and an otherwise healthy patient are diagnostic of ITP. The platelet count cutoff for considering ITP is 100 × 10³/µL as the majority of patients with counts in the 100 to 150 × 10³/µL range will not develop greater thrombocytopenia.¹¹ Also, the platelet count decreases with age (9 × 10³/µL per decade in one study), and this also needs to be factored into the evaluation.¹² The finding of relatives with ITP should raise suspicion for congenital thrombocytopenia.¹³ One should question the patient carefully about drug exposure (see Drug-Induced Thrombocytopenia), especially about over-the-counter medicines, “natural” remedies, or recreational drugs.

There is no laboratory test that rules in ITP; rather, it is a diagnosis of exclusion. The blood smear should be carefully examined for evidence of microangiopathic hemolytic anemias (schistocytes), bone marrow disease (blasts, teardrop cells), or any other evidence of a primary bone marrow disease. In ITP, the platelets can be larger than normal, but finding some platelets the size of red cells should raise the issue of congenital thrombocytopenia.¹⁴ Pseudo-thrombocytopenia, which is the clumping of platelets due to a reaction to the EDTA anticoagulant in the tube, should be excluded. The diagnosis is established by drawing the blood in a citrated (blue-top) tube to perform the platelet count. There is no role for antiplatelet antibody assay because this test lacks sensitivity and specificity. In a patient without a history of autoimmune disease or symptoms, empiric testing for autoimmune disease is not recommended.

Patients who present with ITP should be tested for both HIV and hepatitis C infection.^15,16 These are the most common viral causes of secondary ITP, and both have prognostic and treatment implications. Some authorities also recommend checking thyroid function as hypothyroidism can present or aggravate the thrombocytopenia.

The role of bone marrow examination is controversial.¹⁷ Patients with a classic presentation of ITP (young woman, normal blood smear) do not require a bone marrow exam before therapy is initiated, although patients who do not respond to initial therapy should have a bone marrow aspiration. The rare entity amegakaryocytic thrombocytopenia can present with a clinical picture similar to that of ITP, but amegakaryocytic thrombocytopenia will not respond to steroids. Bone marrow aspiration reveals the absence of megakaryocytes in this entity. It is rare, however, that another hematologic disease is diagnosed in patients with a classic clinical presentation of ITP.

In the future, measurement of thrombopoietin and reticulated platelets may provide clues to the diagnosis.⁴ Patients with ITP paradoxically have normal or only mildly elevated thrombopoietin levels. The finding of a significantly elevated thrombopoietin level should lead to questioning of the diagnosis. One can also measure “reticulated platelets,” which are analogous to red cell reticulocytes. Patients with ITP (or any platelet destructive disorders) will have high levels of reticulated platelets. These tests are not recommended for routine evaluation, but may be helpful in difficult cases.

Treatment

In general, therapy in ITP should be guided by the patient’s signs of bleeding and not by unquestioning adherence to measuring platelet levels,¹⁵ as patients tolerate thrombocytopenia well. It is unusual to have life-threatening bleeding with platelet counts greater than 5 × 10³/µL in the absence of mechanical lesions. Despite the low platelet count in patients with ITP, the overall mortality is estimated to be only 0.3% to 1.3%.¹⁸ It is sobering that in one study the rate of death from infections was twice as high as that from bleeding.¹⁹ Rare patients will have antibodies that interfere with the function of the platelet, and these patients can have profound bleeding with only modestly lowered platelet counts.²⁰ A suggested cut-off for treating newly diagnosed patients is 30 × 10³/µL.²¹

Initial Therapy

The primary therapy of ITP is glucocorticoids, either prednisone or dexamethasone. In the past prednisone at a dose of 60 to 80 mg/day was started at the time of diagnosis (Table 1).

For rapid induction of a response, there are 2 options. A single dose of intravenous immune globulin (IVIG) at 1 g/kg or intravenous anti-D immunoglobulin (anti-D) at 50 to 75 µg/kg can induce a response in more than 80% of patients in 24 to 48 hours.^21,24 IVIG has several drawbacks. It can cause aseptic meningitis, and in patients with vascular disease the increased viscosity can induce ischemia. There is also a considerable fluid load delivered with the IVIG, and it needs to be given over several hours.

The use of anti-D is limited to Rh-positive patients who have not had a splenectomy. It should not be used in patients who are Coombs positive due to the risk of provoking more hemolysis. Rarely anti-D has been reported to cause a severe hemolytic disseminated intravascular coagulation syndrome (1:20,000 patients), which has led to restrictions in its use.²⁵ Although the drug can be rapidly given over 15 minutes, due to these concerns current recommendations are now to observe patients for 8 hours after their dose and to perform a urine dipstick test for blood at 2, 4, and 8 hours. Concerns about this rare but serious side effect have led to a dramatic decrease in the use of anti-D.

For patients who are severely thrombocytopenic and do not respond to initial therapy, there are 2 options for raising the platelet counts. One is to use a combination of IVIG, methylprednisolone, vincristine, and/or anti-D.²⁶ The combination of IVIG and anti-D may be synergistic since these agents block different Fc receptors. A response of 71% has been reported for this 3- or 4-drug combination in a series of 35 patients.²⁶ The other option is to treat with a continuous infusion of platelets (1 unit over 6 hours) and IVIG 1 g/kg for 24 hours. Response rates of 62.7% have been reported with this combination, and this rapid rise in platelets can allow time for other therapies to take effect.^27,28

Patients with severe thrombocytopenia who relapse with reduction of steroids or who do not respond to steroids have several options for further management. Repeated doses of IVIG can transiently raise the platelet count, and some patients may only need several courses of therapy over the course of many months. One study showed that 60% of patients could delay or defer therapy by receiving multiple doses of anti-D. However, 30% of patients did eventually receive splenectomy and 20% of patients required ongoing therapy with anti-D.²⁹ In a randomized trial comparing early use of anti-D to steroids to avoid splenectomy, there was no difference in splenectomy rate (38% versus 42%).³⁰ Finally, an option as mentioned above is to try a 6-month course of pulse dexamethasone 40 mg/day for 4 days, repeated every 28 days.

Options for Refractory ITP

There are multiple options for patients who do not respond to initial ITP therapies. These can be divided into several broad groups: curative therapies (splenectomy and rituximab), thrombopoietin receptor agonists, and anecdotal therapies.

Splenectomy

In patients with severe thrombocytopenia who do not respond or who relapse with lower doses of prednisone, splenectomy should be strongly considered. Splenectomy will induce a good response in 60% to 70% of patients and is durable in most patients. In 2 recently published reviews of splenectomy, the complete response rate was 67% and the total response rate was 88% to 90%%.^8,31 Between 15% and 28% of patients relapsed over 5 years, with most recurrences occurring in the first 2 years. Splenectomy carries a short-term surgical risk, and the life-long risk of increased susceptibility to overwhelming sepsis is discussed below. However, the absolute magnitude of these risks is low and is often lower than the risks of continued prednisone therapy or of continued cytotoxic therapy.

Timing of splenectomy depends on the patient’s presentation. Most patients should be given a 6-month trial of steroids or other therapies before proceeding to splenectomy.³¹ However, patients who persist with severe thrombocytopenia despite initial therapies or who are suffering intolerable side effects from therapy should be considered sooner for splenectomy.³¹ In the George review, multiple factors such as responding to IVIG were found not to be predictive of response to splenectomy.⁸

Method of splenectomy appears not to matter.²¹ Rates of finding accessory spleens are just as high or higher with laparoscopic splenectomy and the patient can recover faster. In patients who are severely thrombocytopenic, open splenectomy can allow for quicker control of the vascular access of the spleen.

Rates of splenectomy in recent years have decreased for many reasons,³² including the acceptance of lower platelet counts in asymptomatic patients and the availability of alternative therapies such as rituximab. In addition, despite abundant data for good outcomes, there is a concern that splenectomy responses are not durable. Although splenectomy will not cure every patient with ITP, splenectomy is the therapy with the most patients, the longest follow-up, and the most consistent rate of cure, and it should be discussed with every ITP patient who does not respond to initial therapy and needs further treatment.

The risk of overwhelming sepsis varies by indications for splenectomy but appears to be about 1%.^33,34 The use of pneumococcal vaccine and recognition of this syndrome have helped reduce the risk. Asplenic patients need to be counseled about the risk of overwhelming infections, should be vaccinated for pneumococcus, meningococcus, and Haemophilus influenzae, and should wear an ID bracelet.^35–37 Patients previously vaccinated for pneumococcus should be re-vaccinated every 3 to 5 years. The role of prophylactic antibiotics in adults is controversial, but patients under the age of 18 should be on penicillin VK 250 mg orally twice daily.

Rituximab

Rituximab has been shown to be very active in ITP. Most studies used the standard dose of 375 mg/m² weekly for 4 weeks, but other studies have shown that 1000 mg twice 14 days apart (ie, on days 1 and 15) resulted in the same response rate and may be more convenient for patients.^38,39 The response time can vary, with patients either showing a rapid response or requiring up to 8 weeks for their counts to go up. Although experience is limited, the response seems to be durable, especially in those patients whose counts rise higher than 150 × 10³/µL; in patients who relapse, a response can be re-induced with a repeat course. Overall the response rate for rituximab is about 60%, but only approximately 20% to 40% of patients will remain in long-term remission.^40–42 There is no evidence yet that “maintenance” therapy or monitoring CD19/CD20 cells can help further the duration of remission.

Whether to give rituximab pre- or post-splenectomy is also uncertain. An advantage of presplenectomy rituximab is that many patients will achieve remission, delaying the need for surgery. Also, rituximab is a good option for patients whose medical conditions put them at high risk for complications with splenectomy. However, it is unknown whether rituximab poses any long-term risks, while the long-term risks of splenectomy are well-defined. Rituximab is the only curative option left for patients who have failed splenectomy and is a reasonable option for these patients.

There is an intriguing trial in which patients were randomly assigned to dexamethasone alone versus dexamethasone plus rituximab upon presentation with ITP; those who were refractory to dexamethasone alone received salvage therapy with dexamethasone plus rituximab.⁴³ The dexamethasone plus rituximab group had an overall higher rate of sustained remission at 6 months than the dexamethasone group, 63% versus 36%. Interestingly, patients who failed their first course of dexamethasone but then were “salvaged” with dexamethasone/rituximab had a similar overall response rate of 56%, suggesting that saving the addition of rituximab for steroid failures may be an effective option.

Although not “chemotherapy,” rituximab is not without risks. Patients can develop infusion reactions, which can be severe in 1% to 2% of patients. In a meta-analysis the fatal reaction rate was 2.9%.⁴⁰ Patients with chronic hepatitis B infections can experience reactivation with rituximab, and thus all patients should be screened before treatment. Finally, the very rare but devastating complication of progressive multifocal leukoencephalopathy has been reported.

Thrombopoietin Receptor Agonists

Although patients with ITP have low platelet counts, studies starting with Dameshek have shown that these patients also have reduced production of platelets.⁴⁴ Despite the very low circulating platelet count, levels of the platelet growth factor thrombopoietin (TPO) are not raised.⁴⁵ Seminal studies with recombinant TPO in the 1990s showed that ITP patients responded to thrombopoietin-stimulating protein, but the formation of anti-TPO antibodies halted trials with the first generation of these agents. Two TPO receptor agonists (TPO-RA) are approved for use in patients with ITP.

Romiplostim. Romiplostim is a peptibody, a combination of a peptide that binds and stimulates the TPO receptor and an Fc domain to extend its half-life.⁴⁶ It is administered in a weekly subcutaneous dose starting at 1 to 3 µg/kg. Use of romiplostim in ITP patients produces a response rate of 80% to 88%, with 87% of patients being able to wean off or decrease other anti-ITP medications.⁴⁷ In a long-term extension study, the response was again high at 87%.⁴⁸ These studies have also shown a reduced incidence of bleeding.

The major side effect of romiplostim seen in clinical trials was marrow reticulin formation, which occurred in up to 5.6% of patients.^47,48 The clinical course in these patients is the development of anemia and a myelophthisic blood smear with teardrop cells and nucleated red cells. These changes appear to reverse with cessation of the drug. The bone marrow shows increased reticulin formation but rarely, if ever, shows the collagen deposition seen with primary myelofibrosis.

Thrombosis has also been seen, with a rate of 0.08 to 0.1 cases per 100 patient-weeks,⁴⁹ but it remains unclear if this is due to the drug, part of the natural history of ITP, or expected complications in older patients undergoing any type of medical therapy. Surprisingly, despite the low platelet counts, patients with ITP in one study had double the risk of venous thrombosis, demonstrating that ITP itself can be a risk factor for thrombosis.⁵⁰ These trials have shown no long-term concerns for other clinical problems such as liver disease.

Eltrombopag. The other available TPO-RA is eltrombopag,⁵¹ an oral agent that stimulates the TPO receptor by binding the transmembrane domain and activating it. The drug is given orally starting at 50 mg/day (25 mg for patients of Asian ancestry or with liver disease) and can be dose escalated to 75 mg/day. The drug needs to be taken on an empty stomach. Eltrombopag has been shown to be effective in chronic ITP, with response rates of 59% to 80% and reduction in use of rescue medications.^47,51,52 As with romiplostim, the incidence of bleeding was also decreased with eltrombopag in these trials.^47,51

Clinical trials demonstrated that eltrombopag shares with romiplostim the risk for marrow fibrosis. A side effect unique to eltrombopag observed in these trials was a 3% to 7% incidence of elevated liver function tests.^21,52 These abnormal findings appeared to resolve in most patients, but liver function tests need to be monitored in patients receiving eltrombopag.

Clinical use. The clearest indication for the use of TPO-RAs is in patients who have failed several therapies and remain symptomatic or are on intolerable doses of other medications such as prednisone. The clear benefits are their relative safety and high rates of success. The main drawback of TPO-RAs is the need for continuing therapy as the platelet count will return to baseline shortly after these agents are stopped. Currently there is no clear indication for one medication over the other. The advantages of romiplostim are great flexibility in dosing (1–10 µg/kg week) and no concerns about drug interaction. The current drawback of romiplostim is the Food and Drug Administration’s requirement for patients to receive the drug from a clinic and not at home. Eltrombopag offers the advantage of oral use, but it has a limited dose range and potential for drug interactions. Both agents have been associated with marrow reticulin formation, although in clinical use this risk appears to be very low.⁵³

Other Options

In the literature there are numerous options for the treatment of ITP.^54,55 Most of these studies are anecdotal, enrolled small number of patients, and sometimes included patients with mild thrombocytopenia, but these therapeutic options can be tried in patients who are refractory to standard therapies and have bleeding. The agents with the greatest amount of supporting data are danazol, vincristine, azathioprine, cyclophosphamide, and fostamatinib.

Danazol 200 mg 4 times daily is thought to downregulate the macrophage Fc receptor. The onset of action may be delayed and a therapeutic trial of up to 4 to 6 months is advised. Danazol is very effective in patients with antiphospholipid antibody syndrome who develop ITP and may be more effective in premenopausal women.⁵⁶ Once a response is seen, danazol should be continued for 6 months and then an attempt to wean the patient off the agent should be made. A partial response can be seen in 70% to 90% of patients, but a complete response is rare.⁵⁴

Vincristine 1.4 mg/m² weekly has a low response rate, but if a response is going to occur, it will occur rapidly within 2 weeks. Thus, a prolonged trial of vincristine is not needed; if no platelet rise is seen in several weeks, the drug should be stopped. Again, partial responses are more common than complete response—50% to 63% versus 0% to 6%.⁵⁴Azathioprine 150 mg orally daily, like danazol, demonstrates a delayed response and requires several months to assess for response. However, 19% to 25% of patients may have a complete response.⁵⁴ It has been reported that the related agent mycophenolate 1000 mg twice daily is also effective in ITP.⁵⁷

Cyclophosphamide 1 g/m² intravenously repeated every 28 days has been reported to have a response rate of up to 40%.⁵⁸ Although considered more aggressive, this is a standard immunosuppressive dose and should be considered in patients with very low platelet counts. Patients who have not responded to single-agent cyclophosphamide may respond to multi-agent chemotherapy with agents such as etoposide and vincristine plus cyclophosphamide.⁵⁹

Fostamatinib, a spleen tyrosine kinase (SYK) inhibitor, is currently under investigation for the treatment of ITP.⁶⁰ This agent prevents phagocytosis of antibody-coated platelets by macrophages. In early studies fostamatinib has been well tolerated at a dose of 150 mg twice daily, with 75% of patients showing a response. Large phase 3 trials are underway, and if the earlier promising results hold up fostamatinib may be a novel option for refractory patients.

A Practical Approach to Refractory ITP

One approach is to divide patients into bleeders, or those with either very low platelet counts (< 5 × 10³/µL) or who have had significant bleeding in the past, and nonbleeders, or those with platelet counts above 5 × 10³/µL and no history of severe bleeding. Bleeders who do not respond adequately to splenectomy should first start with rituximab since it is not cytotoxic and is the only other “curative” therapy (Table 2).

Nonbleeders should be tried on danazol and other relatively safe agents. If this fails, rituximab or TPO-RAs can be considered. Before one considers cytotoxic therapy, the risk of the therapy must be weighed against the risk posed by the thrombocytopenia. The mortality from ITP is fairly low (5%) and is restricted to patients with severe disease. Patients with only moderate thrombocytopenia and no bleeding are better served with conservative management. There is little justification for the use of continuous steroid therapy in this group of patients given the long-term risks of this therapy.

Special Situations

Surgery

Patients with ITP who need surgery either for splenectomy or for other reasons should have their platelet counts raised to a level greater than 20 to 30 × 10³/µL before surgery. Most patients with ITP have increased platelet function and will not have excessive bleeding with these platelet counts. For patients with platelet counts below this level, an infusion of immune globulin or anti-D may rapidly increase the platelet counts. If the surgery is elective, short-term use of TPO-RAs to raise the counts can also be considered.

Pregnancy

Up to 10% of pregnant women will develop low platelet counts during their pregnancy.^61,62 The most common etiology is gestational thrombocytopenia, which is an exaggeration of the lowered platelet count seen in pregnancy. Counts may fall as low as 50 × 10³/µL at the time of delivery. No therapy is required as the fetus is not affected and the mother does not have an increased risk of bleeding. Pregnancy complications such as HELLP syndrome and thrombotic microangiopathies also present with low platelet counts, but these can be diagnosed by history.^61,63

Women with ITP can either develop the disease during pregnancy or have a worsening of the symptoms.⁶⁴ Counts often drop dramatically during the first trimester. Early management should be conservative with low doses of prednisone to keep the count above 10 × 10³/µL.²¹ Immunoglobulin is also effective,⁶⁵ but there are rare reports of pulmonary edema. Rarely patients who are refractory will require splenectomy, which may be safely performed in the second trimester. For delivery the count should be greater than 30 × 10³/µL and for an epidural greater than 50 × 10³/µL.⁶⁴ There are reports of the use of TPO-RAs in pregnancy, and this can be considered for refractory cases.⁶⁶

Most controversy centers on management of the delivery. In the past it was feared that fetal thrombocytopenia could lead to intracranial hemorrhage, and Caesarean section was always recommended. It now appears that most cases of intracranial hemorrhage were due to alloimmune thrombocytopenia and not ITP. Furthermore, the nadir of the baby’s platelet count is not at birth but several days after. It appears the safest course is to proceed with a vaginal or C-section delivery determined by obstetrical indications and then immediately check the baby’s platelet count. If the platelet count is low in the neonate, immunoglobulin will raise the count. Since the neonatal thrombocytopenia is due to passive transfer of maternal antibody, the platelet destruction will abate in 4 to 6 weeks.

Pediatric Patients

The incidence of ITP in children is 2.2 to 5.3 per 100,000 children.¹ There are several distinct differences in pediatric ITP. Most cases will resolve in weeks, with only a minority of patients transforming into chronic ITP (5%–10%). Also, the rates of serious bleeding are lower in children than in adults, with intracranial hemorrhage rates of 0.1% to 0.5% being seen.⁶⁷ For most patients with no or mild bleeding, management now is observation alone regardless of platelet count because it is felt that the risks of therapies are higher than the risk of bleeding.²¹ For patients with bleeding, IVIG, anti-D, or a short course of steroids can be used. Given the risk of overwhelming sepsis, splenectomy is often deferred as long as possible. Rituximab is increasingly being used in children due to concerns about use of agents such a cyclophosphamide or azathioprine in children.⁶⁸ Abundant data on use of TPO-RAs in children showing high response rates and safety support their use, and these should be considered in refractory ITP before any cytotoxic agent.^69–71

Helicobacter Pylori Infection

There has been much interest in the relationship between H. pylori and ITP.^16,72,73H. pylori infections have been associated with a variety of autoimmune diseases, and there is a confusing literature on this infection and ITP. Several meta-analyses have shown that eradication of H. pylori will result in an ITP response rate of 20% to 30%, but responses curiously appear to be limited to certain geographic areas such as Japan and Italy but not the United States. In patients with recalcitrant ITP, especially in geographic areas with high incidence, it may be worthwhile to check for H. pylori infection and treat accordingly if positive.

Drug-Induced Thrombocytopenia

Patients with drug-induced thrombocytopenia present with very low (< 10 × 10³/µL) platelet counts 1 to 3 weeks after starting a new medication.^74–76 In patients with a possible drug-induced thrombocytopenia, the primary therapy is to stop the suspect drug.⁷⁷ If there are multiple new medications, the best approach is to stop any drug that has been strongly associated with thrombocytopenia (Table 3).^74,78,79

Immune globulin, corticosteroids, or intravenous anti‑D have been suggested as useful in drug‑related thrombocytopenia. However, since most of these thrombocytopenic patients recover when the agent is cleared from the body, this therapy is probably not necessary and withholding treatment avoids exposing the patients to the adverse events associated with further therapy.

Evans Syndrome

Evans syndrome is defined as the combination of autoimmune hemolytic anemia (AIHA) and ITP.^80,81 These cytopenias can present simultaneously or sequentially. Patients with Evans syndrome are thought to have a more severe disease process, to be more prone to bleeding, and to be more difficult to treat, but the rarity of this syndrome makes this hard to quantify.

The classic clinical presentation of Evans syndrome is severe anemia and thrombocytopenia. Children with Evans syndrome often have complex immunodeficiencies such as autoimmune lymphoproliferative syndrome.^82,83 In adults, Evans syndrome most often complicates other autoimmune diseases such as lupus. There are increasing reports of Evans syndrome occurring as a complication of T-cell lymphomas. Often the autoimmune disease can predate the lymphoma diagnosis by months or even years.

In theory the diagnostic approach is straightforward by showing a Coombs-positive hemolytic anemia in the setting of a clinical diagnosis of immune thrombocytopenia. The blood smear will show spherocytes and a diminished platelet count. The presence of other abnormal red cell forms should raise the possibility of an alternative diagnosis. It is unclear how vigorously one should search for other underlying diseases. Many patients will already have the diagnosis of an underlying autoimmune disease. The presence of lymphadenopathy should raise concern for lymphoma.

Initial therapy is high-dose steroids (2 mg/kg/day). IVIG should be added if severe thrombocytopenia is present. Patients who cannot be weaned off prednisone or relapse after prednisone should be considered for splenectomy, although these patients are at higher risk of relapsing.⁸⁰ Increasingly rituximab is being used with success.^84,85 For patients who fail splenectomy and rituximab, aggressive immunosuppression should be considered. Increasing data support the benefits of sirolimus, and this should be considered for refractory patients.⁸⁶ For patients with Evans syndrome due to underlying lymphoma, antineoplastic therapy often results in prompt resolution of the symptoms. Recurrence of the autoimmune cytopenias often heralds relapse.

Introduction

Hairy cell leukemia (HCL) is a rare chronic lymphoproliferative disorder, with only approximately 2000 new cases diagnosed in the United States each year.¹ It is now recognized that there are 2 distinct categories of HCL, classic HCL (cHCL) and variant HCL (vHCL), with vHCL now classified as a separate entity under the World Health Organization Classification of Hematopoietic Tumors.² For this reason, the 2 diseases will be discussed separately. However, they do bear many clinical and microscopic similarities and because of this were originally indistinguishable using diagnostic techniques previously available. Even in the modern era using immunophenotypic, molecular, and genetic testing, differentiating between the classic and variant disease subtypes is sometimes difficult.

For cHCL the median age of diagnosis is 55 years, with vHCL occurring in patients who are somewhat older; HCL has been described only in the adult population, with 1 exception.^3,4 There is a 4:1 male predominance, and Caucasians are more frequently affected than other ethnic groups. While the cause of the disease remains largely unknown, it has been observed to occur more frequently in farmers and in persons exposed to pesticides and/or herbicides, petroleum products, and ionizing radiation.⁴ The Institute of Medicine recently updated their position regarding veterans and Agent Orange, stating that there is sufficient evidence of an association between herbicides and chronic lymphoid leukemias (including HCL) to consider these diseases linked to exposure.⁵ Familial forms have also been described that are associated with specific HLA haplotypes, indicating a possible hereditary component.⁶ Most likely, a combination of environmental and genetic factors ultimately contributes to the development of HCL.

In recent years enormous progress has been made with respect to new insights into the biology of cHCL and vHCL, with significant refinement of diagnostic criteria. In addition, tremendous advances have occurred in both treatment and supportive care regimens, which have resulted in a dramatically increased overall life expectancy as well as decreased disease-related morbidity. This has meant that more patients are affected by HCL over time and are more likely to require care for relapsed HCL or associated comorbidities. Although no curative treatment options exist outside of allogeneic transplantation, therapeutic improvements have resulted in patients with cHCL having a life expectancy similar to that of unaffected patients, increasing the need for vigilance to prevent foreseeable complications.

Biology and Patheogenisis

The family of HCLs are chronic B-cell malignancies that account for approximately 2% of all diagnosed leukemias.⁷ The first detailed characterization of HCL as a distinct clinical entity was performed by Dr. Bouroncle and colleagues at the Ohio State University in 1958.⁸ Originally called leukemic reticuloendotheliosis, it was renamed HCL following more detailed description of the unique morphology of these malignant cells.⁹ Significant advances have recently been made in identifying distinctive genetic, immunophenotypic, and morphologic features that distinguish HCL from other B-cell malignancies.

HCL B cells tend to accumulate in the bone marrow, splenic red pulp, and (in some cases) peripheral blood. Unlike other lymphoproliferative disorders, HCL only rarely results in lymphadenopathy. HCL derives its name from the distinct appearance of the malignant hairy cells (Figure). Morphologically, HCL cells are mature, small lymphoid B-cells with a round or oval nucleus and abundant pale blue cytoplasm. Irregular projections of cytoplasm and microvilli give the cells a serrated, “hairy” appearance.¹⁰ The biological significance of these fine hair-like projections remains unknown and is an area of ongoing investigation. Gene expression profiling has revealed that HCL B cells are most similar to splenic marginal zone B cells and memory B cells.^11–13 A recent analysis of common genetic alterations in HCL suggests that the cell of origin is in fact the hematopoietic stem cell.¹⁴

Compared to other hematologic malignancies, the genomic profile of HCL is relatively stable, with few chromosomal defects or translocations observed. A seminal study by Tiacci and colleagues revealed that the BRAF V600E mutation was present in 47 out of 47 cHCL cases examined, results that have since been replicated by other groups, confirming that BRAF V600E is a hallmark mutation in cHCL.¹⁵ The BRAF V600E gain-of-function mutation results in constitutive activation of the serine-threonine protein kinase B-Raf, which regulates the mitogen-activated protein kinase (MAPK)/RAF-MEK-ERK pathway. Indeed, cHCL B cells have elevated MAPK signaling, leading to enhancement of growth and survival.¹⁶ This specific mutation in the BRAF gene is also seen in a number of solid tumor malignancies including melanoma and thyroid cancer, and represents a therapeutic target using BRAF inhibitors already developed to treat these malignancies.¹⁷ Testing for BRAF V600E by polymerase chain reaction or immunohistochemical staining is now routinely performed when HCL is suspected.

While BRAF V600E is identified in nearly all cases of cHCL, it is rare in vHCL.¹⁸ The variant type of HCL was classified as a distinct clinical entity in 2008 and can now often be distinguished from cHCL on the basis of BRAF mutational status, among other differences. Interestingly, in the rare cases of BRAF V600E–negative cHCL, other mutations in BRAF or downstream targets as well as aberrant activation of the RAF-MEK-ERK signaling cascade are observed, indicating that this pathway is critical in HCL and may still represent a viable therapeutic target. Expression of the IGHV4-34 immunoglobulin rearrangement, while more common in vHCL, has also been identified in 10% of cHCL cases and appears to confer poor prognosis.¹⁹ Other mutated genes that have been identified in HCL include CDKN1B, TP53, U2AF1, ARID1A, EZH2, and KDM6A.²⁰

Classic HCL is characterized by the immunophenotypic expression of CD11c, CD25, CD103, and CD123, with kappa or lambda light chain restriction indicating clonality; HCL B cells are generally negative for CD5, CD10, CD23, CD27, and CD79b. In contrast, vHCL often lacks expression of CD25 and CD123.¹⁸ The B-cell receptor (BCR) is expressed on hairy cells and its activation promotes proliferation and survival in vitro.²¹ The role of BCR signaling in B-cell malignancies is increasingly recognized, and therapies that target the BCR and associated signaling molecules offer an attractive treatment strategy.²² HCL B cells also typically express CD19, CD20, CD22, CD79a, CD200, CD1d, and annexin A1. Tartrate-resistant acid phosphatase (TRAP) positivity by immunohistochemistry is a hallmark of cHCL. Interestingly, changes to the patient’s original immunophenotype have been observed following treatment and upon disease recurrence, highlighting the importance of tracking immunophenotype throughout the course of disease.

Diagnosis

Prior to the advent of annual screening evaluations with routine examination of complete blood counts (CBC), patients were most often diagnosed with HCL when they presented with symptoms of the disease such as splenomegaly, infections, or complications of anemia or thrombocytopenia.²³ In the current era, patients are more likely to be incidentally diagnosed when they are found to have an abnormal value on a CBC. Any blood lineage may be affected and patients may have pancytopenia or isolated cytopenias. Of note, monocytopenia is a common finding in cHCL that is not entirely understood. The cells typical of cHCL do not usually circulate in the peripheral blood, but if present would appear as mature lymphocytes with villous cytoplasmic projections, pale blue cytoplasm, and reniform nuclei with open chromatin (Figure).⁹ Even if the morphologic examination is highly suggestive of HCL, additional testing is required to differentiate between cHCL, vHCL, and other hematologic malignancies which may also have cytoplasmic projections. A complete assessment of the immunophenotype, molecular profile, and cytogenetic features is required to arrive at this diagnosis.

The international Hairy Cell Leukemia Foundation recently published consensus guidelines for the diagnosis and treatment of HCL.²⁴ These guidelines recommend that patients undergo examination of the peripheral blood for morphology and immunophenotyping and further recommend obtaining bone marrow core and aspirate biopsy samples for immunophenotyping via immunohistochemical staining and flow cytometry. The characteristic immunophenotype of cHCL is a population of monoclonal B lymphocytes which co-express CD19, CD20, CD11c, CD25, CD103, and CD123. Variant HCL is characterized by a very similar immunophenotype but is usually negative for CD25 and CD123. It is notable that CD25 positivity may be lost following treatment, and the absence of this marker should not be used as the sole basis of a cHCL versus vHCL diagnosis. Because marrow fibrosis in HCL may prevent a marrow aspirate from being obtained, many of the key diagnostic studies are performed on the core biopsy, including morphological evaluation and immunohistochemical stains such as CD20 (a pan-B cell antigen), annexin-1 (an anti-inflammatory protein expressed only in cHCL), and VE1 (a BRAF V600E stain).

As noted above, recurrent cytogenetic abnormalities have now been identified that may inform the diagnosis or prognosis of HCL. Next-generation sequencing and other testing of the genetic landscape are taking on a larger role in subtype differentiation, and it is likely that future guidelines will recommend evaluation for significant mutations. Given that BRAF V600E mutation status is a key feature of cHCL and is absent in vHCL, it is important to perform this testing at the time of diagnosis whenever possible. The mutation may be detected via VE1 immunohistochemical staining, allele-specific polymerase chain reaction, or next-generation sequencing. Other less sensitive tests exist but are utilized less frequently.

Minimal Residual Disease

There is currently no accepted standard for minimal residual disease (MRD) monitoring in HCL. While detection of MRD has been clearly associated with increased risk of disease progression, cHCL cells typically do not circulate in the peripheral blood, limiting the use of peripheral blood immunophenotyping for quantitative MRD assessment. For quantitative monitoring of marrow involvement by HCL, immunohistochemical staining of the bone marrow core biopsy is usually required. Staining may be performed for CD20, or, in patients who have received anti-CD20 therapy, DBA.44, VE-1, or CD79a. There is currently not a consensus regarding what level of disease involvement constitutes MRD. One group studied this issue and found that relapse could be predicted by evaluating MRD by percentage of positive cells in the marrow by immunohistochemical staining, with less than 1% involvement having the lowest risk for disease relapse and greater than 5% having the highest risk for disease relapse.²⁵ A recent study evaluated MRD patterns in the peripheral blood of 32 cHCL patients who had completed frontline therapy. This group performed flow cytometry on the peripheral blood of patients at 1, 3, 6, and 12 months following therapy. All patients had achieved a complete response with initial therapy and peripheral blood MRD negativity at the completion of therapy. At a median follow-up of 100 months post therapy, 5 patients converted from peripheral blood–MRD negative to peripheral blood–MRD positive, and 6 patients developed overt disease progression. In all patients who progressed, progression was preceded by an increase in detectable peripheral blood MRD cells.²⁶ Although larger studies are needed, peripheral blood flow cytometric monitoring for MRD may be a useful adjunct to predict ongoing response or impending relapse. In addition, newer, more sensitive methods of disease monitoring may ultimately supplant flow cytometry.

Risk Stratification

Although much progress has been made in the risk stratification profiling of hematologic malignancies in general, HCL has unfortunately lagged behind in this effort. The most recent risk stratification analysis was performed in 1982 by Jansen and colleagues.²⁷ This group of researchers performed a retrospective analysis of 391 HCL patients treated at 22 centers. One of the central questions in their analysis was survival time from diagnosis in patients who had not yet undergone splenectomy (a standard treatment at the time). This group consisted of a total of 154 patients. As this study predated modern pathological and molecular testing, clinical and laboratory features were examined, and these mostly consisted of physical exam findings and analysis of the peripheral blood. This group found that several factors influenced the survival of these patients, including duration of symptoms prior to diagnosis, the degree of splenomegaly, hemoglobin level, and number of hairy cells in the peripheral blood. However, because of interobserver variation for the majority of these variables, only hemoglobin and spleen size were included in the proportional hazard model. Using only these 2 variables, the authors were able to determine 3 clinical stages for HCL (Table 1). The stages were found to correlate with median survival: patients with stage 1 disease had a median survival not reached at 72 months, but patients with stage 2 disease had a median survival of 18 months, which decreased to only 12 months in patients with stage 3 disease.

Because the majority of patients with HCL in the modern era will be diagnosed prior to reaching stage 3, a risk stratification system incorporating clinical features, laboratory parameters, and molecular and genetic testing is of considerable interest and is a subject of ongoing research. Ultimately, the goal will be to identify patients at higher risk of early relapse so that more intensive therapies can be applied to initial treatment that will result in longer treatment-free intervals.

Treatment

Because there is no curative treatment for either cHCL or vHCL outside allogeneic transplantation, and it is not clear that early treatment leads to better outcomes in HCL, patients do not always receive treatment at the time of diagnosis or relapse. The general consensus is that patients should be treated if there is a declining trend in hematologic parameters or they experience symptoms from the disease.²⁴ Current consensus guidelines recommend treatment when any of the following hematologic parameters are met: hemoglobin less than 11 g/dL, platelet count less than 100 × 10³/µL, or absolute neutrophil count less than 1000/µL.²⁴ These parameters are surrogate markers that indicate compromised bone marrow function. Cytopenias may also be caused by splenomegaly, and symptomatic splenomegaly with or without cytopenias is an indication for treatment. A small number of patients with HCL (approximately 10%) do not require immediate therapy after diagnosis and are monitored by their provider until treatment is indicated.

First-Line Therapy

Despite advances in targeted therapies for HCL, because no treatment has been shown to extend the treatment-free interval longer than chemotherapy, treatment with a purine nucleoside analog is usually the recommended first-line therapy. This includes either cladribine or pentostatin. Both agents appear to be equally effective, and the choice of therapy is determined by the treating physician based on his or her experience. Cladribine administration has been studied using a number of different schedules and routes: intravenous continuous infusion (0.1 mg/kg) for 7 days, intravenous infusion (0.14 mg/kg/day) over 2 hours on a 5-day regimen, or alternatively subcutaneously (0.1–0.14 mg/kg/day) on a once-per-day or once-per-week regimen (Table 2).^28,29

Unlike cHCL, vHCL remains difficult to treat and early disease progression is common. The best outcomes have been seen in patients who have received combination chemo-immunotherapy such as purine nucleoside analog therapy plus rituximab or bendamustine plus rituximab.³¹ One pilot study of bendamustine plus rituximab in 12 patients found an overall response rate of 100%, with the majority of patients achieving a complete response.³¹ For patients who achieved a complete response, the median duration of response had not been reached, but patients achieving only a partial response had a median duration of response of only 20 months, indicating there is a subgroup of patients who will require a different treatment approach.³² A randomized phase 2 trial of rituximab with either pentostatin or bendamustine is ongoing.³³

Assessment of Response

Response assessment involves physical examination for estimation of spleen size, assessment of hematologic parameters, and a bone marrow biopsy for evaluation of marrow response. It is recommended that the bone marrow biopsy be performed 4 to 6 months following cladribine administration, or after completion of 12 doses of pentostatin. Detailed response assessment criteria are shown in Table 3.

Second-Line Therapy

Although the majority of patients treated with purine analogs will achieve durable remissions, approximately 40% of patients will eventually require second-line therapy. Criteria for treatment at relapse are the same as the criteria for initial therapy, including symptomatic disease or progressive anemia, thrombocytopenia, or neutropenia. The choice of treatment is based on clinical parameters and the duration of the previous remission. If the initial remission was longer than 65 months and the patient is eligible to receive chemotherapy, re-treatment with initial therapy is recommended. For a remission between 24 and 65 months, re-treatment with a purine analog combined with an anti-CD20 monoclonal antibody may be considered.³⁴ If the first remission is shorter than 24 months, confirmation of the original diagnosis as well as consideration for testing for additional mutations with therapeutic targets (BRAF V600E, MAP2K1) should be considered before a treatment decision is made. For these patients, alternative therapies, including investigational agents, should be considered.²⁴

Monoclonal antibody therapy has been studied in both the up-front setting and in relapsed or refractory HCL.³⁵ An initial study of 15 patients with relapsed HCL found an overall response rate of 80%, with 8 patients achieving a complete response. A subsequent study of 26 patients who relapsed after cladribine therapy found an overall response rate of 80%, with a complete response rate of 32%. Median relapse-free survival was 27 months.³⁶ Ravandi and others studied rituximab in the up-front setting in combination with cladribine, and found an overall response rate of 100%, including in patients with vHCL. At the time of publication of the study results, the median survival had not been reached.³⁷ As has been seen with other lymphoid malignancies, concurrent therapy with rituximab appears to enhance the activity of the agent with which it is combined. While its use in the up-front setting remains an area of active investigation, there is a clear role for chemo-immunotherapy in the relapsed setting.

In patients with cHCL, excellent results including complete remissions have been reported with the use of BRAF inhibitors, both as a single agent and when combined with anti-CD20 therapy. The 2 commercially available BRAF inhibitors are vemurafenib and dabrafenib, and both have been tested in relapsed cHCL.^38,39 The first study of vemurafenib was reported by Tiacci and colleagues, who found an overall response rate of 96% after a median of 8 weeks and a 100% response rate after a median of 12 weeks, with complete response rates up to 42%.³⁸ The median relapse-free survival was 23 months (decreasing to only 6 months in patients who achieved only a partial remission), indicating that these agents will likely need to be administered in combination with other effective therapies with non-overlapping toxicities. Vemurafenib has been administered concurrently with rituximab, and preliminary results of this combination therapy showed early rates of complete responses.⁴⁰ Dabrafenib has been reported for use as a single agent in cHCL and clinical trials are underway evaluating its efficacy when administered with trametinib, a MEK inhibitor.^39,41 Of note, patients receiving BRAF inhibitors frequently develop cutaneous complications of RAF inhibition including cutaneous squamous cell carcinomas and keratoacanthomas, and close dermatologic surveillance is required.

Variant HCL does not harbor the BRAF V600E mutation, but up to half of patients have been found to have mutations of MAP2K1, which upregulates MEK1 expression.⁴² Trametinib is approved by the US Food and Drug Administration for the treatment of patients with melanoma at a dose of 2 mg orally daily, and has been successfully used to treat 1 patient with vHCL.⁴³ Further evaluation of this targeted therapy is underway.

Ibrutinib, a Bruton tyrosine kinase inhibitor, and moxetumomab pasudotox, an immunotoxin conjugate, are currently being studied in National Institutes of Health–sponsored multi-institutional trials for patients with HCL. Ibrutinib is administered orally at 420 mg per day until relapse.⁴⁴ Moxetumomab pasudotox was tested at different doses between 5 and 50 μg/kg intravenously every other day for 3 doses for up to 16 cycles unless they experienced disease progression or developed neutralizing antibodies.⁴⁵ Both agents have been shown to have significant activity in cHCL and vHCL and will likely be included in the treatment armamentarium once trials are completed. Second-line therapy options are summarized in Table 4.

Complications and Supportive Care

The complications of HCL may be separated into the pre-, intra-, and post-treatment periods. At the time of diagnosis and prior to the initiation of therapy, marrow infiltration by HCL frequently leads to cytopenias which cause symptomatic anemia, infection, and/or bleeding complications. Many patients develop splenomegaly, which may further lower the blood counts and which is experienced as abdominal fullness or distention, with early satiety leading to weight loss. Patients may also experience constitutional symptoms with fatigue, fevers in the absence of infection, and unintentional weight loss even without splenomegaly.

For patients who initiate therapy with purine nucleoside analogs, the early part of treatment is associated with the greatest risk of morbidity and mortality. Chemotherapy leads to both immunosuppression (altered cellular immunity) as well as myelosuppression. Thus, patients who are already in need of treatment because of disease-related cytopenias will experience an abrupt and sometimes significant decline in the peripheral blood counts. The treatment period prior to recovery of neutrophils requires the greatest vigilance. Because patients are profoundly immunocompromised, febrile neutropenia is a common complication leading to hospital admission and the cause is often difficult to identify. Treatment with broad-spectrum antibiotics, investigation for opportunistic and viral infections, and considerations for antifungal prophylaxis or therapy are required in this setting. It is recommended that all patients treated with purine nucleoside analogs receive prophylactic antimicrobials for herpes simplex virus and varicella zoster virus, as well as prophylaxis against Pneumocystis jirovecii. Unfortunately, growth factor support has not proven successful in this patient population but is not contraindicated.⁴⁶

Following successful completion of therapy, patients may remain functionally immunocompromised for a significant period of time even with a normal neutrophil count. Monitoring of the CD4 count may help to determine when prophylactic antimicrobials may be discontinued. A CD4 count greater than 200 cells/µL is generally considered to be adequate for prevention of opportunistic infections. Although immunizations have not been well studied in HCL, it is recommended that patients receive annual influenza immunizations as well as age-appropriate immunizations against Streptococcus pneumoniae and other infectious illnesses as indicated. Live viral vaccines such as the currently available herpes zoster vaccine can lead to infections in this patient population and are not recommended.

Like many hematologic malignancies, HCL may be associated with comorbid conditions related to immune dysfunction. There is a known association with an increased risk of second primary malignancies, which may predate the diagnosis of HCL.⁴⁷ Therefore, it is recommended that patients continue annual cancer screenings as well as undergo prompt evaluation for potential symptoms of second malignancies. In addition, it is thought that there may be an increased risk for autoimmune disorders such as inflammatory arthritis or immune-mediated cytopenias. One case-control study found a possible association between autoimmune diseases and HCL, noting that at times these diseases are diagnosed concurrently.⁴⁸ However, because of the rarity of the disease it has been difficult to quantify these associated conditions in a systematic way. There is currently an international patient data registry under development for the systematic study of HCL and its complications which may answer many of these questions.

Survivorship and quality of life are important considerations in chronic diseases. It is not uncommon for patients to develop anxiety related to the trauma of diagnosis and treatment, especially when intensive care has been required. Patients may have lingering fears regarding concerns of developing infections due to exposure to ill persons or fears regarding risk of relapse and need for re-treatment. A proactive approach with partnership with psychosocial oncology may be of benefit, especially when symptoms of post-traumatic stress disorder are evident.

Conclusion

HCL is a rare, chronic lymphoid malignancy that is now subclassified into classic and variant HCL. Further investigations into the disease subtypes will allow more precise disease definitions, and these studies are underway. Renewed efforts toward updated risk stratification and clinical staging systems will be important aspects of these investigations. Refinements in treatment and supportive care have resulted in greatly improved overall survival, which has translated into larger numbers of people living with HCL. However, new treatment paradigms for vHCL are needed as the progression-free survival in this disease remains significantly lower than that of cHCL. Future efforts toward understanding survivorship issues and management of long-term treatment and disease-related complications will be critical for ensuring good quality of life for patients living with HCL.

Introduction

Hairy cell leukemia (HCL) is a rare chronic lymphoproliferative disorder, with only approximately 2000 new cases diagnosed in the United States each year.¹ It is now recognized that there are 2 distinct categories of HCL, classic HCL (cHCL) and variant HCL (vHCL), with vHCL now classified as a separate entity under the World Health Organization Classification of Hematopoietic Tumors.² For this reason, the 2 diseases will be discussed separately. However, they do bear many clinical and microscopic similarities and because of this were originally indistinguishable using diagnostic techniques previously available. Even in the modern era using immunophenotypic, molecular, and genetic testing, differentiating between the classic and variant disease subtypes is sometimes difficult.

For cHCL the median age of diagnosis is 55 years, with vHCL occurring in patients who are somewhat older; HCL has been described only in the adult population, with 1 exception.^3,4 There is a 4:1 male predominance, and Caucasians are more frequently affected than other ethnic groups. While the cause of the disease remains largely unknown, it has been observed to occur more frequently in farmers and in persons exposed to pesticides and/or herbicides, petroleum products, and ionizing radiation.⁴ The Institute of Medicine recently updated their position regarding veterans and Agent Orange, stating that there is sufficient evidence of an association between herbicides and chronic lymphoid leukemias (including HCL) to consider these diseases linked to exposure.⁵ Familial forms have also been described that are associated with specific HLA haplotypes, indicating a possible hereditary component.⁶ Most likely, a combination of environmental and genetic factors ultimately contributes to the development of HCL.

In recent years enormous progress has been made with respect to new insights into the biology of cHCL and vHCL, with significant refinement of diagnostic criteria. In addition, tremendous advances have occurred in both treatment and supportive care regimens, which have resulted in a dramatically increased overall life expectancy as well as decreased disease-related morbidity. This has meant that more patients are affected by HCL over time and are more likely to require care for relapsed HCL or associated comorbidities. Although no curative treatment options exist outside of allogeneic transplantation, therapeutic improvements have resulted in patients with cHCL having a life expectancy similar to that of unaffected patients, increasing the need for vigilance to prevent foreseeable complications.

Biology and Patheogenisis

The family of HCLs are chronic B-cell malignancies that account for approximately 2% of all diagnosed leukemias.⁷ The first detailed characterization of HCL as a distinct clinical entity was performed by Dr. Bouroncle and colleagues at the Ohio State University in 1958.⁸ Originally called leukemic reticuloendotheliosis, it was renamed HCL following more detailed description of the unique morphology of these malignant cells.⁹ Significant advances have recently been made in identifying distinctive genetic, immunophenotypic, and morphologic features that distinguish HCL from other B-cell malignancies.

HCL B cells tend to accumulate in the bone marrow, splenic red pulp, and (in some cases) peripheral blood. Unlike other lymphoproliferative disorders, HCL only rarely results in lymphadenopathy. HCL derives its name from the distinct appearance of the malignant hairy cells (Figure). Morphologically, HCL cells are mature, small lymphoid B-cells with a round or oval nucleus and abundant pale blue cytoplasm. Irregular projections of cytoplasm and microvilli give the cells a serrated, “hairy” appearance.¹⁰ The biological significance of these fine hair-like projections remains unknown and is an area of ongoing investigation. Gene expression profiling has revealed that HCL B cells are most similar to splenic marginal zone B cells and memory B cells.^11–13 A recent analysis of common genetic alterations in HCL suggests that the cell of origin is in fact the hematopoietic stem cell.¹⁴

Compared to other hematologic malignancies, the genomic profile of HCL is relatively stable, with few chromosomal defects or translocations observed. A seminal study by Tiacci and colleagues revealed that the BRAF V600E mutation was present in 47 out of 47 cHCL cases examined, results that have since been replicated by other groups, confirming that BRAF V600E is a hallmark mutation in cHCL.¹⁵ The BRAF V600E gain-of-function mutation results in constitutive activation of the serine-threonine protein kinase B-Raf, which regulates the mitogen-activated protein kinase (MAPK)/RAF-MEK-ERK pathway. Indeed, cHCL B cells have elevated MAPK signaling, leading to enhancement of growth and survival.¹⁶ This specific mutation in the BRAF gene is also seen in a number of solid tumor malignancies including melanoma and thyroid cancer, and represents a therapeutic target using BRAF inhibitors already developed to treat these malignancies.¹⁷ Testing for BRAF V600E by polymerase chain reaction or immunohistochemical staining is now routinely performed when HCL is suspected.

While BRAF V600E is identified in nearly all cases of cHCL, it is rare in vHCL.¹⁸ The variant type of HCL was classified as a distinct clinical entity in 2008 and can now often be distinguished from cHCL on the basis of BRAF mutational status, among other differences. Interestingly, in the rare cases of BRAF V600E–negative cHCL, other mutations in BRAF or downstream targets as well as aberrant activation of the RAF-MEK-ERK signaling cascade are observed, indicating that this pathway is critical in HCL and may still represent a viable therapeutic target. Expression of the IGHV4-34 immunoglobulin rearrangement, while more common in vHCL, has also been identified in 10% of cHCL cases and appears to confer poor prognosis.¹⁹ Other mutated genes that have been identified in HCL include CDKN1B, TP53, U2AF1, ARID1A, EZH2, and KDM6A.²⁰

Classic HCL is characterized by the immunophenotypic expression of CD11c, CD25, CD103, and CD123, with kappa or lambda light chain restriction indicating clonality; HCL B cells are generally negative for CD5, CD10, CD23, CD27, and CD79b. In contrast, vHCL often lacks expression of CD25 and CD123.¹⁸ The B-cell receptor (BCR) is expressed on hairy cells and its activation promotes proliferation and survival in vitro.²¹ The role of BCR signaling in B-cell malignancies is increasingly recognized, and therapies that target the BCR and associated signaling molecules offer an attractive treatment strategy.²² HCL B cells also typically express CD19, CD20, CD22, CD79a, CD200, CD1d, and annexin A1. Tartrate-resistant acid phosphatase (TRAP) positivity by immunohistochemistry is a hallmark of cHCL. Interestingly, changes to the patient’s original immunophenotype have been observed following treatment and upon disease recurrence, highlighting the importance of tracking immunophenotype throughout the course of disease.

Diagnosis

Prior to the advent of annual screening evaluations with routine examination of complete blood counts (CBC), patients were most often diagnosed with HCL when they presented with symptoms of the disease such as splenomegaly, infections, or complications of anemia or thrombocytopenia.²³ In the current era, patients are more likely to be incidentally diagnosed when they are found to have an abnormal value on a CBC. Any blood lineage may be affected and patients may have pancytopenia or isolated cytopenias. Of note, monocytopenia is a common finding in cHCL that is not entirely understood. The cells typical of cHCL do not usually circulate in the peripheral blood, but if present would appear as mature lymphocytes with villous cytoplasmic projections, pale blue cytoplasm, and reniform nuclei with open chromatin (Figure).⁹ Even if the morphologic examination is highly suggestive of HCL, additional testing is required to differentiate between cHCL, vHCL, and other hematologic malignancies which may also have cytoplasmic projections. A complete assessment of the immunophenotype, molecular profile, and cytogenetic features is required to arrive at this diagnosis.

The international Hairy Cell Leukemia Foundation recently published consensus guidelines for the diagnosis and treatment of HCL.²⁴ These guidelines recommend that patients undergo examination of the peripheral blood for morphology and immunophenotyping and further recommend obtaining bone marrow core and aspirate biopsy samples for immunophenotyping via immunohistochemical staining and flow cytometry. The characteristic immunophenotype of cHCL is a population of monoclonal B lymphocytes which co-express CD19, CD20, CD11c, CD25, CD103, and CD123. Variant HCL is characterized by a very similar immunophenotype but is usually negative for CD25 and CD123. It is notable that CD25 positivity may be lost following treatment, and the absence of this marker should not be used as the sole basis of a cHCL versus vHCL diagnosis. Because marrow fibrosis in HCL may prevent a marrow aspirate from being obtained, many of the key diagnostic studies are performed on the core biopsy, including morphological evaluation and immunohistochemical stains such as CD20 (a pan-B cell antigen), annexin-1 (an anti-inflammatory protein expressed only in cHCL), and VE1 (a BRAF V600E stain).

As noted above, recurrent cytogenetic abnormalities have now been identified that may inform the diagnosis or prognosis of HCL. Next-generation sequencing and other testing of the genetic landscape are taking on a larger role in subtype differentiation, and it is likely that future guidelines will recommend evaluation for significant mutations. Given that BRAF V600E mutation status is a key feature of cHCL and is absent in vHCL, it is important to perform this testing at the time of diagnosis whenever possible. The mutation may be detected via VE1 immunohistochemical staining, allele-specific polymerase chain reaction, or next-generation sequencing. Other less sensitive tests exist but are utilized less frequently.

Minimal Residual Disease

There is currently no accepted standard for minimal residual disease (MRD) monitoring in HCL. While detection of MRD has been clearly associated with increased risk of disease progression, cHCL cells typically do not circulate in the peripheral blood, limiting the use of peripheral blood immunophenotyping for quantitative MRD assessment. For quantitative monitoring of marrow involvement by HCL, immunohistochemical staining of the bone marrow core biopsy is usually required. Staining may be performed for CD20, or, in patients who have received anti-CD20 therapy, DBA.44, VE-1, or CD79a. There is currently not a consensus regarding what level of disease involvement constitutes MRD. One group studied this issue and found that relapse could be predicted by evaluating MRD by percentage of positive cells in the marrow by immunohistochemical staining, with less than 1% involvement having the lowest risk for disease relapse and greater than 5% having the highest risk for disease relapse.²⁵ A recent study evaluated MRD patterns in the peripheral blood of 32 cHCL patients who had completed frontline therapy. This group performed flow cytometry on the peripheral blood of patients at 1, 3, 6, and 12 months following therapy. All patients had achieved a complete response with initial therapy and peripheral blood MRD negativity at the completion of therapy. At a median follow-up of 100 months post therapy, 5 patients converted from peripheral blood–MRD negative to peripheral blood–MRD positive, and 6 patients developed overt disease progression. In all patients who progressed, progression was preceded by an increase in detectable peripheral blood MRD cells.²⁶ Although larger studies are needed, peripheral blood flow cytometric monitoring for MRD may be a useful adjunct to predict ongoing response or impending relapse. In addition, newer, more sensitive methods of disease monitoring may ultimately supplant flow cytometry.

Risk Stratification

Although much progress has been made in the risk stratification profiling of hematologic malignancies in general, HCL has unfortunately lagged behind in this effort. The most recent risk stratification analysis was performed in 1982 by Jansen and colleagues.²⁷ This group of researchers performed a retrospective analysis of 391 HCL patients treated at 22 centers. One of the central questions in their analysis was survival time from diagnosis in patients who had not yet undergone splenectomy (a standard treatment at the time). This group consisted of a total of 154 patients. As this study predated modern pathological and molecular testing, clinical and laboratory features were examined, and these mostly consisted of physical exam findings and analysis of the peripheral blood. This group found that several factors influenced the survival of these patients, including duration of symptoms prior to diagnosis, the degree of splenomegaly, hemoglobin level, and number of hairy cells in the peripheral blood. However, because of interobserver variation for the majority of these variables, only hemoglobin and spleen size were included in the proportional hazard model. Using only these 2 variables, the authors were able to determine 3 clinical stages for HCL (Table 1). The stages were found to correlate with median survival: patients with stage 1 disease had a median survival not reached at 72 months, but patients with stage 2 disease had a median survival of 18 months, which decreased to only 12 months in patients with stage 3 disease.

Because the majority of patients with HCL in the modern era will be diagnosed prior to reaching stage 3, a risk stratification system incorporating clinical features, laboratory parameters, and molecular and genetic testing is of considerable interest and is a subject of ongoing research. Ultimately, the goal will be to identify patients at higher risk of early relapse so that more intensive therapies can be applied to initial treatment that will result in longer treatment-free intervals.

Treatment

Because there is no curative treatment for either cHCL or vHCL outside allogeneic transplantation, and it is not clear that early treatment leads to better outcomes in HCL, patients do not always receive treatment at the time of diagnosis or relapse. The general consensus is that patients should be treated if there is a declining trend in hematologic parameters or they experience symptoms from the disease.²⁴ Current consensus guidelines recommend treatment when any of the following hematologic parameters are met: hemoglobin less than 11 g/dL, platelet count less than 100 × 10³/µL, or absolute neutrophil count less than 1000/µL.²⁴ These parameters are surrogate markers that indicate compromised bone marrow function. Cytopenias may also be caused by splenomegaly, and symptomatic splenomegaly with or without cytopenias is an indication for treatment. A small number of patients with HCL (approximately 10%) do not require immediate therapy after diagnosis and are monitored by their provider until treatment is indicated.

First-Line Therapy

Despite advances in targeted therapies for HCL, because no treatment has been shown to extend the treatment-free interval longer than chemotherapy, treatment with a purine nucleoside analog is usually the recommended first-line therapy. This includes either cladribine or pentostatin. Both agents appear to be equally effective, and the choice of therapy is determined by the treating physician based on his or her experience. Cladribine administration has been studied using a number of different schedules and routes: intravenous continuous infusion (0.1 mg/kg) for 7 days, intravenous infusion (0.14 mg/kg/day) over 2 hours on a 5-day regimen, or alternatively subcutaneously (0.1–0.14 mg/kg/day) on a once-per-day or once-per-week regimen (Table 2).^28,29

Unlike cHCL, vHCL remains difficult to treat and early disease progression is common. The best outcomes have been seen in patients who have received combination chemo-immunotherapy such as purine nucleoside analog therapy plus rituximab or bendamustine plus rituximab.³¹ One pilot study of bendamustine plus rituximab in 12 patients found an overall response rate of 100%, with the majority of patients achieving a complete response.³¹ For patients who achieved a complete response, the median duration of response had not been reached, but patients achieving only a partial response had a median duration of response of only 20 months, indicating there is a subgroup of patients who will require a different treatment approach.³² A randomized phase 2 trial of rituximab with either pentostatin or bendamustine is ongoing.³³

Assessment of Response

Response assessment involves physical examination for estimation of spleen size, assessment of hematologic parameters, and a bone marrow biopsy for evaluation of marrow response. It is recommended that the bone marrow biopsy be performed 4 to 6 months following cladribine administration, or after completion of 12 doses of pentostatin. Detailed response assessment criteria are shown in Table 3.

Second-Line Therapy

Although the majority of patients treated with purine analogs will achieve durable remissions, approximately 40% of patients will eventually require second-line therapy. Criteria for treatment at relapse are the same as the criteria for initial therapy, including symptomatic disease or progressive anemia, thrombocytopenia, or neutropenia. The choice of treatment is based on clinical parameters and the duration of the previous remission. If the initial remission was longer than 65 months and the patient is eligible to receive chemotherapy, re-treatment with initial therapy is recommended. For a remission between 24 and 65 months, re-treatment with a purine analog combined with an anti-CD20 monoclonal antibody may be considered.³⁴ If the first remission is shorter than 24 months, confirmation of the original diagnosis as well as consideration for testing for additional mutations with therapeutic targets (BRAF V600E, MAP2K1) should be considered before a treatment decision is made. For these patients, alternative therapies, including investigational agents, should be considered.²⁴

Monoclonal antibody therapy has been studied in both the up-front setting and in relapsed or refractory HCL.³⁵ An initial study of 15 patients with relapsed HCL found an overall response rate of 80%, with 8 patients achieving a complete response. A subsequent study of 26 patients who relapsed after cladribine therapy found an overall response rate of 80%, with a complete response rate of 32%. Median relapse-free survival was 27 months.³⁶ Ravandi and others studied rituximab in the up-front setting in combination with cladribine, and found an overall response rate of 100%, including in patients with vHCL. At the time of publication of the study results, the median survival had not been reached.³⁷ As has been seen with other lymphoid malignancies, concurrent therapy with rituximab appears to enhance the activity of the agent with which it is combined. While its use in the up-front setting remains an area of active investigation, there is a clear role for chemo-immunotherapy in the relapsed setting.

In patients with cHCL, excellent results including complete remissions have been reported with the use of BRAF inhibitors, both as a single agent and when combined with anti-CD20 therapy. The 2 commercially available BRAF inhibitors are vemurafenib and dabrafenib, and both have been tested in relapsed cHCL.^38,39 The first study of vemurafenib was reported by Tiacci and colleagues, who found an overall response rate of 96% after a median of 8 weeks and a 100% response rate after a median of 12 weeks, with complete response rates up to 42%.³⁸ The median relapse-free survival was 23 months (decreasing to only 6 months in patients who achieved only a partial remission), indicating that these agents will likely need to be administered in combination with other effective therapies with non-overlapping toxicities. Vemurafenib has been administered concurrently with rituximab, and preliminary results of this combination therapy showed early rates of complete responses.⁴⁰ Dabrafenib has been reported for use as a single agent in cHCL and clinical trials are underway evaluating its efficacy when administered with trametinib, a MEK inhibitor.^39,41 Of note, patients receiving BRAF inhibitors frequently develop cutaneous complications of RAF inhibition including cutaneous squamous cell carcinomas and keratoacanthomas, and close dermatologic surveillance is required.

Variant HCL does not harbor the BRAF V600E mutation, but up to half of patients have been found to have mutations of MAP2K1, which upregulates MEK1 expression.⁴² Trametinib is approved by the US Food and Drug Administration for the treatment of patients with melanoma at a dose of 2 mg orally daily, and has been successfully used to treat 1 patient with vHCL.⁴³ Further evaluation of this targeted therapy is underway.

Ibrutinib, a Bruton tyrosine kinase inhibitor, and moxetumomab pasudotox, an immunotoxin conjugate, are currently being studied in National Institutes of Health–sponsored multi-institutional trials for patients with HCL. Ibrutinib is administered orally at 420 mg per day until relapse.⁴⁴ Moxetumomab pasudotox was tested at different doses between 5 and 50 μg/kg intravenously every other day for 3 doses for up to 16 cycles unless they experienced disease progression or developed neutralizing antibodies.⁴⁵ Both agents have been shown to have significant activity in cHCL and vHCL and will likely be included in the treatment armamentarium once trials are completed. Second-line therapy options are summarized in Table 4.

Complications and Supportive Care

The complications of HCL may be separated into the pre-, intra-, and post-treatment periods. At the time of diagnosis and prior to the initiation of therapy, marrow infiltration by HCL frequently leads to cytopenias which cause symptomatic anemia, infection, and/or bleeding complications. Many patients develop splenomegaly, which may further lower the blood counts and which is experienced as abdominal fullness or distention, with early satiety leading to weight loss. Patients may also experience constitutional symptoms with fatigue, fevers in the absence of infection, and unintentional weight loss even without splenomegaly.

For patients who initiate therapy with purine nucleoside analogs, the early part of treatment is associated with the greatest risk of morbidity and mortality. Chemotherapy leads to both immunosuppression (altered cellular immunity) as well as myelosuppression. Thus, patients who are already in need of treatment because of disease-related cytopenias will experience an abrupt and sometimes significant decline in the peripheral blood counts. The treatment period prior to recovery of neutrophils requires the greatest vigilance. Because patients are profoundly immunocompromised, febrile neutropenia is a common complication leading to hospital admission and the cause is often difficult to identify. Treatment with broad-spectrum antibiotics, investigation for opportunistic and viral infections, and considerations for antifungal prophylaxis or therapy are required in this setting. It is recommended that all patients treated with purine nucleoside analogs receive prophylactic antimicrobials for herpes simplex virus and varicella zoster virus, as well as prophylaxis against Pneumocystis jirovecii. Unfortunately, growth factor support has not proven successful in this patient population but is not contraindicated.⁴⁶

Following successful completion of therapy, patients may remain functionally immunocompromised for a significant period of time even with a normal neutrophil count. Monitoring of the CD4 count may help to determine when prophylactic antimicrobials may be discontinued. A CD4 count greater than 200 cells/µL is generally considered to be adequate for prevention of opportunistic infections. Although immunizations have not been well studied in HCL, it is recommended that patients receive annual influenza immunizations as well as age-appropriate immunizations against Streptococcus pneumoniae and other infectious illnesses as indicated. Live viral vaccines such as the currently available herpes zoster vaccine can lead to infections in this patient population and are not recommended.

Like many hematologic malignancies, HCL may be associated with comorbid conditions related to immune dysfunction. There is a known association with an increased risk of second primary malignancies, which may predate the diagnosis of HCL.⁴⁷ Therefore, it is recommended that patients continue annual cancer screenings as well as undergo prompt evaluation for potential symptoms of second malignancies. In addition, it is thought that there may be an increased risk for autoimmune disorders such as inflammatory arthritis or immune-mediated cytopenias. One case-control study found a possible association between autoimmune diseases and HCL, noting that at times these diseases are diagnosed concurrently.⁴⁸ However, because of the rarity of the disease it has been difficult to quantify these associated conditions in a systematic way. There is currently an international patient data registry under development for the systematic study of HCL and its complications which may answer many of these questions.

Survivorship and quality of life are important considerations in chronic diseases. It is not uncommon for patients to develop anxiety related to the trauma of diagnosis and treatment, especially when intensive care has been required. Patients may have lingering fears regarding concerns of developing infections due to exposure to ill persons or fears regarding risk of relapse and need for re-treatment. A proactive approach with partnership with psychosocial oncology may be of benefit, especially when symptoms of post-traumatic stress disorder are evident.

Conclusion

HCL is a rare, chronic lymphoid malignancy that is now subclassified into classic and variant HCL. Further investigations into the disease subtypes will allow more precise disease definitions, and these studies are underway. Renewed efforts toward updated risk stratification and clinical staging systems will be important aspects of these investigations. Refinements in treatment and supportive care have resulted in greatly improved overall survival, which has translated into larger numbers of people living with HCL. However, new treatment paradigms for vHCL are needed as the progression-free survival in this disease remains significantly lower than that of cHCL. Future efforts toward understanding survivorship issues and management of long-term treatment and disease-related complications will be critical for ensuring good quality of life for patients living with HCL.

Introduction

Hairy cell leukemia (HCL) is a rare chronic lymphoproliferative disorder, with only approximately 2000 new cases diagnosed in the United States each year.¹ It is now recognized that there are 2 distinct categories of HCL, classic HCL (cHCL) and variant HCL (vHCL), with vHCL now classified as a separate entity under the World Health Organization Classification of Hematopoietic Tumors.² For this reason, the 2 diseases will be discussed separately. However, they do bear many clinical and microscopic similarities and because of this were originally indistinguishable using diagnostic techniques previously available. Even in the modern era using immunophenotypic, molecular, and genetic testing, differentiating between the classic and variant disease subtypes is sometimes difficult.

For cHCL the median age of diagnosis is 55 years, with vHCL occurring in patients who are somewhat older; HCL has been described only in the adult population, with 1 exception.^3,4 There is a 4:1 male predominance, and Caucasians are more frequently affected than other ethnic groups. While the cause of the disease remains largely unknown, it has been observed to occur more frequently in farmers and in persons exposed to pesticides and/or herbicides, petroleum products, and ionizing radiation.⁴ The Institute of Medicine recently updated their position regarding veterans and Agent Orange, stating that there is sufficient evidence of an association between herbicides and chronic lymphoid leukemias (including HCL) to consider these diseases linked to exposure.⁵ Familial forms have also been described that are associated with specific HLA haplotypes, indicating a possible hereditary component.⁶ Most likely, a combination of environmental and genetic factors ultimately contributes to the development of HCL.

In recent years enormous progress has been made with respect to new insights into the biology of cHCL and vHCL, with significant refinement of diagnostic criteria. In addition, tremendous advances have occurred in both treatment and supportive care regimens, which have resulted in a dramatically increased overall life expectancy as well as decreased disease-related morbidity. This has meant that more patients are affected by HCL over time and are more likely to require care for relapsed HCL or associated comorbidities. Although no curative treatment options exist outside of allogeneic transplantation, therapeutic improvements have resulted in patients with cHCL having a life expectancy similar to that of unaffected patients, increasing the need for vigilance to prevent foreseeable complications.

Biology and Patheogenisis

The family of HCLs are chronic B-cell malignancies that account for approximately 2% of all diagnosed leukemias.⁷ The first detailed characterization of HCL as a distinct clinical entity was performed by Dr. Bouroncle and colleagues at the Ohio State University in 1958.⁸ Originally called leukemic reticuloendotheliosis, it was renamed HCL following more detailed description of the unique morphology of these malignant cells.⁹ Significant advances have recently been made in identifying distinctive genetic, immunophenotypic, and morphologic features that distinguish HCL from other B-cell malignancies.

HCL B cells tend to accumulate in the bone marrow, splenic red pulp, and (in some cases) peripheral blood. Unlike other lymphoproliferative disorders, HCL only rarely results in lymphadenopathy. HCL derives its name from the distinct appearance of the malignant hairy cells (Figure). Morphologically, HCL cells are mature, small lymphoid B-cells with a round or oval nucleus and abundant pale blue cytoplasm. Irregular projections of cytoplasm and microvilli give the cells a serrated, “hairy” appearance.¹⁰ The biological significance of these fine hair-like projections remains unknown and is an area of ongoing investigation. Gene expression profiling has revealed that HCL B cells are most similar to splenic marginal zone B cells and memory B cells.^11–13 A recent analysis of common genetic alterations in HCL suggests that the cell of origin is in fact the hematopoietic stem cell.¹⁴

Compared to other hematologic malignancies, the genomic profile of HCL is relatively stable, with few chromosomal defects or translocations observed. A seminal study by Tiacci and colleagues revealed that the BRAF V600E mutation was present in 47 out of 47 cHCL cases examined, results that have since been replicated by other groups, confirming that BRAF V600E is a hallmark mutation in cHCL.¹⁵ The BRAF V600E gain-of-function mutation results in constitutive activation of the serine-threonine protein kinase B-Raf, which regulates the mitogen-activated protein kinase (MAPK)/RAF-MEK-ERK pathway. Indeed, cHCL B cells have elevated MAPK signaling, leading to enhancement of growth and survival.¹⁶ This specific mutation in the BRAF gene is also seen in a number of solid tumor malignancies including melanoma and thyroid cancer, and represents a therapeutic target using BRAF inhibitors already developed to treat these malignancies.¹⁷ Testing for BRAF V600E by polymerase chain reaction or immunohistochemical staining is now routinely performed when HCL is suspected.

While BRAF V600E is identified in nearly all cases of cHCL, it is rare in vHCL.¹⁸ The variant type of HCL was classified as a distinct clinical entity in 2008 and can now often be distinguished from cHCL on the basis of BRAF mutational status, among other differences. Interestingly, in the rare cases of BRAF V600E–negative cHCL, other mutations in BRAF or downstream targets as well as aberrant activation of the RAF-MEK-ERK signaling cascade are observed, indicating that this pathway is critical in HCL and may still represent a viable therapeutic target. Expression of the IGHV4-34 immunoglobulin rearrangement, while more common in vHCL, has also been identified in 10% of cHCL cases and appears to confer poor prognosis.¹⁹ Other mutated genes that have been identified in HCL include CDKN1B, TP53, U2AF1, ARID1A, EZH2, and KDM6A.²⁰

Classic HCL is characterized by the immunophenotypic expression of CD11c, CD25, CD103, and CD123, with kappa or lambda light chain restriction indicating clonality; HCL B cells are generally negative for CD5, CD10, CD23, CD27, and CD79b. In contrast, vHCL often lacks expression of CD25 and CD123.¹⁸ The B-cell receptor (BCR) is expressed on hairy cells and its activation promotes proliferation and survival in vitro.²¹ The role of BCR signaling in B-cell malignancies is increasingly recognized, and therapies that target the BCR and associated signaling molecules offer an attractive treatment strategy.²² HCL B cells also typically express CD19, CD20, CD22, CD79a, CD200, CD1d, and annexin A1. Tartrate-resistant acid phosphatase (TRAP) positivity by immunohistochemistry is a hallmark of cHCL. Interestingly, changes to the patient’s original immunophenotype have been observed following treatment and upon disease recurrence, highlighting the importance of tracking immunophenotype throughout the course of disease.

Diagnosis

Prior to the advent of annual screening evaluations with routine examination of complete blood counts (CBC), patients were most often diagnosed with HCL when they presented with symptoms of the disease such as splenomegaly, infections, or complications of anemia or thrombocytopenia.²³ In the current era, patients are more likely to be incidentally diagnosed when they are found to have an abnormal value on a CBC. Any blood lineage may be affected and patients may have pancytopenia or isolated cytopenias. Of note, monocytopenia is a common finding in cHCL that is not entirely understood. The cells typical of cHCL do not usually circulate in the peripheral blood, but if present would appear as mature lymphocytes with villous cytoplasmic projections, pale blue cytoplasm, and reniform nuclei with open chromatin (Figure).⁹ Even if the morphologic examination is highly suggestive of HCL, additional testing is required to differentiate between cHCL, vHCL, and other hematologic malignancies which may also have cytoplasmic projections. A complete assessment of the immunophenotype, molecular profile, and cytogenetic features is required to arrive at this diagnosis.

The international Hairy Cell Leukemia Foundation recently published consensus guidelines for the diagnosis and treatment of HCL.²⁴ These guidelines recommend that patients undergo examination of the peripheral blood for morphology and immunophenotyping and further recommend obtaining bone marrow core and aspirate biopsy samples for immunophenotyping via immunohistochemical staining and flow cytometry. The characteristic immunophenotype of cHCL is a population of monoclonal B lymphocytes which co-express CD19, CD20, CD11c, CD25, CD103, and CD123. Variant HCL is characterized by a very similar immunophenotype but is usually negative for CD25 and CD123. It is notable that CD25 positivity may be lost following treatment, and the absence of this marker should not be used as the sole basis of a cHCL versus vHCL diagnosis. Because marrow fibrosis in HCL may prevent a marrow aspirate from being obtained, many of the key diagnostic studies are performed on the core biopsy, including morphological evaluation and immunohistochemical stains such as CD20 (a pan-B cell antigen), annexin-1 (an anti-inflammatory protein expressed only in cHCL), and VE1 (a BRAF V600E stain).

As noted above, recurrent cytogenetic abnormalities have now been identified that may inform the diagnosis or prognosis of HCL. Next-generation sequencing and other testing of the genetic landscape are taking on a larger role in subtype differentiation, and it is likely that future guidelines will recommend evaluation for significant mutations. Given that BRAF V600E mutation status is a key feature of cHCL and is absent in vHCL, it is important to perform this testing at the time of diagnosis whenever possible. The mutation may be detected via VE1 immunohistochemical staining, allele-specific polymerase chain reaction, or next-generation sequencing. Other less sensitive tests exist but are utilized less frequently.

Minimal Residual Disease

There is currently no accepted standard for minimal residual disease (MRD) monitoring in HCL. While detection of MRD has been clearly associated with increased risk of disease progression, cHCL cells typically do not circulate in the peripheral blood, limiting the use of peripheral blood immunophenotyping for quantitative MRD assessment. For quantitative monitoring of marrow involvement by HCL, immunohistochemical staining of the bone marrow core biopsy is usually required. Staining may be performed for CD20, or, in patients who have received anti-CD20 therapy, DBA.44, VE-1, or CD79a. There is currently not a consensus regarding what level of disease involvement constitutes MRD. One group studied this issue and found that relapse could be predicted by evaluating MRD by percentage of positive cells in the marrow by immunohistochemical staining, with less than 1% involvement having the lowest risk for disease relapse and greater than 5% having the highest risk for disease relapse.²⁵ A recent study evaluated MRD patterns in the peripheral blood of 32 cHCL patients who had completed frontline therapy. This group performed flow cytometry on the peripheral blood of patients at 1, 3, 6, and 12 months following therapy. All patients had achieved a complete response with initial therapy and peripheral blood MRD negativity at the completion of therapy. At a median follow-up of 100 months post therapy, 5 patients converted from peripheral blood–MRD negative to peripheral blood–MRD positive, and 6 patients developed overt disease progression. In all patients who progressed, progression was preceded by an increase in detectable peripheral blood MRD cells.²⁶ Although larger studies are needed, peripheral blood flow cytometric monitoring for MRD may be a useful adjunct to predict ongoing response or impending relapse. In addition, newer, more sensitive methods of disease monitoring may ultimately supplant flow cytometry.

Risk Stratification

Although much progress has been made in the risk stratification profiling of hematologic malignancies in general, HCL has unfortunately lagged behind in this effort. The most recent risk stratification analysis was performed in 1982 by Jansen and colleagues.²⁷ This group of researchers performed a retrospective analysis of 391 HCL patients treated at 22 centers. One of the central questions in their analysis was survival time from diagnosis in patients who had not yet undergone splenectomy (a standard treatment at the time). This group consisted of a total of 154 patients. As this study predated modern pathological and molecular testing, clinical and laboratory features were examined, and these mostly consisted of physical exam findings and analysis of the peripheral blood. This group found that several factors influenced the survival of these patients, including duration of symptoms prior to diagnosis, the degree of splenomegaly, hemoglobin level, and number of hairy cells in the peripheral blood. However, because of interobserver variation for the majority of these variables, only hemoglobin and spleen size were included in the proportional hazard model. Using only these 2 variables, the authors were able to determine 3 clinical stages for HCL (Table 1). The stages were found to correlate with median survival: patients with stage 1 disease had a median survival not reached at 72 months, but patients with stage 2 disease had a median survival of 18 months, which decreased to only 12 months in patients with stage 3 disease.

Because the majority of patients with HCL in the modern era will be diagnosed prior to reaching stage 3, a risk stratification system incorporating clinical features, laboratory parameters, and molecular and genetic testing is of considerable interest and is a subject of ongoing research. Ultimately, the goal will be to identify patients at higher risk of early relapse so that more intensive therapies can be applied to initial treatment that will result in longer treatment-free intervals.

Treatment

Because there is no curative treatment for either cHCL or vHCL outside allogeneic transplantation, and it is not clear that early treatment leads to better outcomes in HCL, patients do not always receive treatment at the time of diagnosis or relapse. The general consensus is that patients should be treated if there is a declining trend in hematologic parameters or they experience symptoms from the disease.²⁴ Current consensus guidelines recommend treatment when any of the following hematologic parameters are met: hemoglobin less than 11 g/dL, platelet count less than 100 × 10³/µL, or absolute neutrophil count less than 1000/µL.²⁴ These parameters are surrogate markers that indicate compromised bone marrow function. Cytopenias may also be caused by splenomegaly, and symptomatic splenomegaly with or without cytopenias is an indication for treatment. A small number of patients with HCL (approximately 10%) do not require immediate therapy after diagnosis and are monitored by their provider until treatment is indicated.

First-Line Therapy

Despite advances in targeted therapies for HCL, because no treatment has been shown to extend the treatment-free interval longer than chemotherapy, treatment with a purine nucleoside analog is usually the recommended first-line therapy. This includes either cladribine or pentostatin. Both agents appear to be equally effective, and the choice of therapy is determined by the treating physician based on his or her experience. Cladribine administration has been studied using a number of different schedules and routes: intravenous continuous infusion (0.1 mg/kg) for 7 days, intravenous infusion (0.14 mg/kg/day) over 2 hours on a 5-day regimen, or alternatively subcutaneously (0.1–0.14 mg/kg/day) on a once-per-day or once-per-week regimen (Table 2).^28,29

Unlike cHCL, vHCL remains difficult to treat and early disease progression is common. The best outcomes have been seen in patients who have received combination chemo-immunotherapy such as purine nucleoside analog therapy plus rituximab or bendamustine plus rituximab.³¹ One pilot study of bendamustine plus rituximab in 12 patients found an overall response rate of 100%, with the majority of patients achieving a complete response.³¹ For patients who achieved a complete response, the median duration of response had not been reached, but patients achieving only a partial response had a median duration of response of only 20 months, indicating there is a subgroup of patients who will require a different treatment approach.³² A randomized phase 2 trial of rituximab with either pentostatin or bendamustine is ongoing.³³

Assessment of Response

Response assessment involves physical examination for estimation of spleen size, assessment of hematologic parameters, and a bone marrow biopsy for evaluation of marrow response. It is recommended that the bone marrow biopsy be performed 4 to 6 months following cladribine administration, or after completion of 12 doses of pentostatin. Detailed response assessment criteria are shown in Table 3.

Second-Line Therapy

Although the majority of patients treated with purine analogs will achieve durable remissions, approximately 40% of patients will eventually require second-line therapy. Criteria for treatment at relapse are the same as the criteria for initial therapy, including symptomatic disease or progressive anemia, thrombocytopenia, or neutropenia. The choice of treatment is based on clinical parameters and the duration of the previous remission. If the initial remission was longer than 65 months and the patient is eligible to receive chemotherapy, re-treatment with initial therapy is recommended. For a remission between 24 and 65 months, re-treatment with a purine analog combined with an anti-CD20 monoclonal antibody may be considered.³⁴ If the first remission is shorter than 24 months, confirmation of the original diagnosis as well as consideration for testing for additional mutations with therapeutic targets (BRAF V600E, MAP2K1) should be considered before a treatment decision is made. For these patients, alternative therapies, including investigational agents, should be considered.²⁴

Monoclonal antibody therapy has been studied in both the up-front setting and in relapsed or refractory HCL.³⁵ An initial study of 15 patients with relapsed HCL found an overall response rate of 80%, with 8 patients achieving a complete response. A subsequent study of 26 patients who relapsed after cladribine therapy found an overall response rate of 80%, with a complete response rate of 32%. Median relapse-free survival was 27 months.³⁶ Ravandi and others studied rituximab in the up-front setting in combination with cladribine, and found an overall response rate of 100%, including in patients with vHCL. At the time of publication of the study results, the median survival had not been reached.³⁷ As has been seen with other lymphoid malignancies, concurrent therapy with rituximab appears to enhance the activity of the agent with which it is combined. While its use in the up-front setting remains an area of active investigation, there is a clear role for chemo-immunotherapy in the relapsed setting.

In patients with cHCL, excellent results including complete remissions have been reported with the use of BRAF inhibitors, both as a single agent and when combined with anti-CD20 therapy. The 2 commercially available BRAF inhibitors are vemurafenib and dabrafenib, and both have been tested in relapsed cHCL.^38,39 The first study of vemurafenib was reported by Tiacci and colleagues, who found an overall response rate of 96% after a median of 8 weeks and a 100% response rate after a median of 12 weeks, with complete response rates up to 42%.³⁸ The median relapse-free survival was 23 months (decreasing to only 6 months in patients who achieved only a partial remission), indicating that these agents will likely need to be administered in combination with other effective therapies with non-overlapping toxicities. Vemurafenib has been administered concurrently with rituximab, and preliminary results of this combination therapy showed early rates of complete responses.⁴⁰ Dabrafenib has been reported for use as a single agent in cHCL and clinical trials are underway evaluating its efficacy when administered with trametinib, a MEK inhibitor.^39,41 Of note, patients receiving BRAF inhibitors frequently develop cutaneous complications of RAF inhibition including cutaneous squamous cell carcinomas and keratoacanthomas, and close dermatologic surveillance is required.

Variant HCL does not harbor the BRAF V600E mutation, but up to half of patients have been found to have mutations of MAP2K1, which upregulates MEK1 expression.⁴² Trametinib is approved by the US Food and Drug Administration for the treatment of patients with melanoma at a dose of 2 mg orally daily, and has been successfully used to treat 1 patient with vHCL.⁴³ Further evaluation of this targeted therapy is underway.

Ibrutinib, a Bruton tyrosine kinase inhibitor, and moxetumomab pasudotox, an immunotoxin conjugate, are currently being studied in National Institutes of Health–sponsored multi-institutional trials for patients with HCL. Ibrutinib is administered orally at 420 mg per day until relapse.⁴⁴ Moxetumomab pasudotox was tested at different doses between 5 and 50 μg/kg intravenously every other day for 3 doses for up to 16 cycles unless they experienced disease progression or developed neutralizing antibodies.⁴⁵ Both agents have been shown to have significant activity in cHCL and vHCL and will likely be included in the treatment armamentarium once trials are completed. Second-line therapy options are summarized in Table 4.

Complications and Supportive Care

The complications of HCL may be separated into the pre-, intra-, and post-treatment periods. At the time of diagnosis and prior to the initiation of therapy, marrow infiltration by HCL frequently leads to cytopenias which cause symptomatic anemia, infection, and/or bleeding complications. Many patients develop splenomegaly, which may further lower the blood counts and which is experienced as abdominal fullness or distention, with early satiety leading to weight loss. Patients may also experience constitutional symptoms with fatigue, fevers in the absence of infection, and unintentional weight loss even without splenomegaly.

For patients who initiate therapy with purine nucleoside analogs, the early part of treatment is associated with the greatest risk of morbidity and mortality. Chemotherapy leads to both immunosuppression (altered cellular immunity) as well as myelosuppression. Thus, patients who are already in need of treatment because of disease-related cytopenias will experience an abrupt and sometimes significant decline in the peripheral blood counts. The treatment period prior to recovery of neutrophils requires the greatest vigilance. Because patients are profoundly immunocompromised, febrile neutropenia is a common complication leading to hospital admission and the cause is often difficult to identify. Treatment with broad-spectrum antibiotics, investigation for opportunistic and viral infections, and considerations for antifungal prophylaxis or therapy are required in this setting. It is recommended that all patients treated with purine nucleoside analogs receive prophylactic antimicrobials for herpes simplex virus and varicella zoster virus, as well as prophylaxis against Pneumocystis jirovecii. Unfortunately, growth factor support has not proven successful in this patient population but is not contraindicated.⁴⁶

Following successful completion of therapy, patients may remain functionally immunocompromised for a significant period of time even with a normal neutrophil count. Monitoring of the CD4 count may help to determine when prophylactic antimicrobials may be discontinued. A CD4 count greater than 200 cells/µL is generally considered to be adequate for prevention of opportunistic infections. Although immunizations have not been well studied in HCL, it is recommended that patients receive annual influenza immunizations as well as age-appropriate immunizations against Streptococcus pneumoniae and other infectious illnesses as indicated. Live viral vaccines such as the currently available herpes zoster vaccine can lead to infections in this patient population and are not recommended.

Like many hematologic malignancies, HCL may be associated with comorbid conditions related to immune dysfunction. There is a known association with an increased risk of second primary malignancies, which may predate the diagnosis of HCL.⁴⁷ Therefore, it is recommended that patients continue annual cancer screenings as well as undergo prompt evaluation for potential symptoms of second malignancies. In addition, it is thought that there may be an increased risk for autoimmune disorders such as inflammatory arthritis or immune-mediated cytopenias. One case-control study found a possible association between autoimmune diseases and HCL, noting that at times these diseases are diagnosed concurrently.⁴⁸ However, because of the rarity of the disease it has been difficult to quantify these associated conditions in a systematic way. There is currently an international patient data registry under development for the systematic study of HCL and its complications which may answer many of these questions.

Survivorship and quality of life are important considerations in chronic diseases. It is not uncommon for patients to develop anxiety related to the trauma of diagnosis and treatment, especially when intensive care has been required. Patients may have lingering fears regarding concerns of developing infections due to exposure to ill persons or fears regarding risk of relapse and need for re-treatment. A proactive approach with partnership with psychosocial oncology may be of benefit, especially when symptoms of post-traumatic stress disorder are evident.

Conclusion

HCL is a rare, chronic lymphoid malignancy that is now subclassified into classic and variant HCL. Further investigations into the disease subtypes will allow more precise disease definitions, and these studies are underway. Renewed efforts toward updated risk stratification and clinical staging systems will be important aspects of these investigations. Refinements in treatment and supportive care have resulted in greatly improved overall survival, which has translated into larger numbers of people living with HCL. However, new treatment paradigms for vHCL are needed as the progression-free survival in this disease remains significantly lower than that of cHCL. Future efforts toward understanding survivorship issues and management of long-term treatment and disease-related complications will be critical for ensuring good quality of life for patients living with HCL.

Introduction

Over the past several decades, while the incidence of breast cancer has increased, breast cancer mortality has decreased. This decrease is likely due to both early detection and advances in systemic therapy. However, with more widespread use of screening mammography, there are increasing concerns about potential overdiagnosis of cancer.¹ One key challenge is that breast cancer is a heterogeneous disease. Improved tools for determining breast cancer biology can help physicians individualize treatments. Patients with low-risk cancers can be approached with less aggressive treatments, thus preventing unnecessary toxicities, while those with higher-risk cancers remain treated appropriately with more aggressive therapies.

Traditionally, adjuvant chemotherapy was recommended based on tumor features such as stage (tumor size, regional nodal involvement), grade, expression of hormone receptors (estrogen receptor [ER] and progesterone receptor [PR]) and human epidermal growth factor receptor-2 (HER2), and patient features (age, menopausal status). However, this approach is not accurate enough to guide individualized treatment approaches, which are based on the risk for recurrence and the reduction in this risk that can be achieved with various systemic treatments. In particular, women with low-risk hormone receptor (HR)–positive, HER2-negative breast cancers could be spared the toxicities of cytotoxic chemotherapies without compromising the prognosis.

Beyond chemotherapy, endocrine therapies also have risks, especially when given over extended periods of time. Recently, extended endocrine therapy has been shown to prevent late recurrences of HR-positive breast cancers. In the National Cancer Institute of Canada Clinical Trials Group’s MA.17R study, extended endocrine therapy with letrozole for a total of 10 years (beyond 5 years of an aromatase inhibitor [AI]) decreased the risk for breast cancer recurrence or the occurrence of contralateral breast cancer by 34%.² However, the overall survival was similar between the 2 groups and the disease-free survival benefits were not confirmed in other studies.^3–5 Identifying the subgroup of patients who benefit from this extended AI therapy is important in the era of personalized medicine. Several tumor genomic assays have been developed to provide additional prognostic and predictive information with the goal of individualizing adjuvant therapies for breast cancer. Although assays are also being evaluated in HER2-positive and triple-negative breast cancer, this review will focus on HR-positive, HER2-negative breast cancer.

Tests for Guiding Adjuvant Chemotherapy Decisions

Case Study

Initial Presentation

A 54-year-old postmenopausal woman with no significant past medical history presents with an abnormal screening mammogram, which shows a focal asymmetry in the 10 o’clock position at middle depth of the left breast. Further work-up with a diagnostic mammogram and ultrasound of the left breast shows a suspicious hypoechoic solid mass with irregular margins measuring 17 mm. The patient undergoes an ultrasound-guided core needle biopsy of the suspicious mass, the results of which are consistent with an invasive ductal carcinoma, Nottingham grade 2, ER strongly positive (95%), PR weakly positive (5%), HER2-negative, and Ki-67 of 15%. She undergoes a left partial mastectomy and sentinel lymph node biopsy, with final pathology demonstrating a single focus of invasive ductal carcinoma, measuring 2.2 cm in greatest dimension with no evidence of lymphovascular invasion. Margins are clear and 2 sentinel lymph nodes are negative for metastatic disease (final pathologic stage IIA, pT2 pN0 cM0). She is referred to medical oncology to discuss adjuvant systemic therapy.

• Can additional testing be used to determine prognosis and guide systemic therapy recommendations for early-stage HR-positive/HER2-negative breast cancer?

After a diagnosis of early-stage breast cancer, the key clinical question faced by the patient and medical oncologist is: what is the individual’s risk for a metastatic breast cancer recurrence and thus the risk for death due to breast cancer? Once the risk for recurrence is established, systemic adjuvant chemotherapy, endocrine therapy, and/or HER2-directed therapy are considered based on the receptor status (ER/PR and HER2) to reduce this risk. HR-positive, HER2-negative breast cancer is the most common type of breast cancer. Although adjuvant endocrine therapy has significantly reduced the risk for recurrence and improved survival for patients with HR-positive breast cancer,⁶ the role of adjuvant chemotherapy for this subset of breast cancer remains unclear. Prior to genomic testing, the recommendation for adjuvant chemotherapy for HR-positive/HER2-negative tumors was primarily based on patient age and tumor stage and grade. However, chemotherapy overtreatment remained a concern given the potential short- and long-term risks of chemotherapy. Further studies into HR-positive/HER2-negative tumors have shown that these tumors can be divided into 2 main subtypes, luminal A and luminal B.⁷ These subtypes represent unique biology and differ in terms of prognosis and response to endocrine therapy and chemotherapy. Luminal A tumors are strongly endocrine responsive and have a good prognosis, while luminal B tumors are less endocrine responsive and are associated with a poorer prognosis; the addition of adjuvant chemotherapy is often considered for luminal B tumors.⁸ Several tests, including tumor genomic assays, are now available to help with delineating the tumor subtype and aid in decision-making regarding adjuvant chemotherapy for HR-positive/HER2-negative breast cancers.

Ki-67 Assays, Including IHC4 and PEPI

Proliferation is a hallmark of cancer cells.⁹ Ki-67, a nuclear nonhistone protein whose expression varies in intensity throughout the cell cycle, has been used as a measurement of tumor cell proliferation.¹⁰ Two large meta-analyses have demonstrated that high Ki-67 expression in breast tumors is independently associated with worse disease-free and overall survival rates.^11,12 Ki-67 expression has also been used to classify HR-positive tumors as luminal A or B. After classifying tumor subtypes based on intrinsic gene expression profiling, Cheang and colleagues determined that a Ki-67 cut point of 13.25% differentiated luminal A and B tumors.¹³ However, the ideal cut point for Ki-67 remains unclear, as the sensitivity and specificity in this study was 77% and 78%, respectively. Others have combined Ki-67 with standard ER, PR, and HER2 testing. This immunohistochemical 4 (IHC4) score, which weighs each of these variables, was validated in postmenopausal patients from the ATAC (Arimidex, Tamoxifen, Alone or in Combination) trial who had ER-positive tumors and did not receive chemotherapy.¹⁴ The prognostic information from the IHC4 was similar to that seen with the 21-gene recurrence score (Oncotype DX), which is discussed later in this article. The key challenge with Ki-67 testing currently is the lack of a validated test methodology and intra-observer variability in interpreting the Ki-67 results.¹⁵ Recent series have suggested that Ki-67 be considered as a continuous marker rather than a set cut point.¹⁶ These issues continue to impact the clinical utility of Ki-67 for decision-making for adjuvant chemotherapy.

Ki-67 and the preoperative endocrine prognostic index (PEPI) score have been explored in the neoadjuvant setting to separate postmenopausal women with endocrine-sensitive versus intrinsically resistant disease and identify patients at risk for recurrent disease.¹⁷ The on-treatment levels of Ki-67 in response to endocrine therapy have been shown to be more prognostic than baseline values, and a decrease in Ki-67 as early as 2 weeks after initiation of neoadjuvant endocrine therapy is associated with endocrine-sensitive tumors and improved outcome. The PEPI score was developed through retrospective analysis of the P024 trial¹⁸ to evaluate the relationship between post-neoadjuvant endocrine therapy tumor characteristics and risk for early relapse. The score was subsequently validated in an independent data set from the IMPACT (Immediate Preoperative Anastrozole, Tamoxifen, or Combined with Tamoxifen) trial.¹⁹ Patients with low pathological stage (0 or 1) and a favorable biomarker profile (PEPI score 0) at surgery had the best prognosis in the absence of chemotherapy. On the other hand, higher pathological stage at surgery and a poor biomarker profile with loss of ER positivity or persistently elevated Ki-67 (PEPI score of 3) identified de novo endocrine-resistant tumors that are higher risk for early relapse.²⁰ The ongoing Alliance A011106 ALTERNATE trial (ALTernate approaches for clinical stage II or III Estrogen Receptor positive breast cancer NeoAdjuvant TrEatment in postmenopausal women, NCT01953588) is a phase 3 study to prospectively test this hypothesis.

21-Gene Recurrence Score (Onco type DX Assay)

The 21-gene Oncotype DX assay is conducted on paraffin-embedded tumor tissue and measures the expression of 16 cancer related genes and 5 reference genes using quantitative polymerase chain reaction (PCR). The genes included in this assay are mainly related to proliferation (including Ki-67), invasion, and HER2 or estrogen signaling.²¹ Originally, the 21-gene recurrence score assay was analyzed as a prognostic biomarker tool in a prospective-retrospective biomarker substudy of the National Surgical Adjuvant Breast and Bowel Project (NSABP) B-14 clinical trial in which patients with node-negative, ER-positive tumors were randomly assigned to receive tamoxifen or placebo without chemotherapy.²² Using the standard reported values of low risk (< 18), intermediate risk (18–30), or high risk (≥ 31) for recurrence, among the tamoxifen-treated patients, cancers with a high-risk recurrence score had a significantly worse rate of distant recurrence and overall survival.²¹ Inferior breast cancer survival in cancers with a high recurrence score was also confirmed in other series of endocrine-treated patients with node-negative and node-positive disease.^23–25

The predictive utility of the 21-gene recurrence score for endocrine therapy has also been evaluated. A comparison of the placebo- and tamoxifen-treated patients from the NSABP B-14 trial demonstrated that the 21-gene recurrence score predicted benefit from tamoxifen in cancers with low- or intermediate-risk recurrence scores.²⁶ However, there was no benefit from the use of tamoxifen over placebo in cancers with high-risk recurrence scores. To date, this intriguing data has not been prospectively confirmed, and thus the 21-gene recurrence score is not used to avoid endocrine therapy.

The 21-gene recurrence score is primarily used by oncologists to aid in decision-making regarding adjuvant chemotherapy in patients with node-negative and node-positive (with up to 3 positive lymph nodes), HR-positive/HER2-negative breast cancers. The predictive utility of the 21-gene recurrence score for adjuvant chemotherapy was initially tested using tumor samples from the NSABP B-20 study. This study initially compared adjuvant tamoxifen alone with tamoxifen plus chemotherapy in patients with node-negative, HR-positive tumors. The prospective-retrospective biomarker analysis showed that the patients with high-risk 21-gene recurrence scores benefited from the addition of chemotherapy, whereas those with low or intermediate risk did not have an improved freedom from distant recurrence with chemotherapy.²⁷ Similarly, an analysis from the prospective phase 3 Southwest Oncology Group (SWOG) 8814 trial comparing tamoxifen to tamoxifen with chemotherapy showed that for node-positive tumors, chemotherapy benefit was only seen in those with high 21-gene recurrence scores.²⁴

Prospective studies are now starting to report results regarding the predictive role of the 21-gene recurrence score. The TAILORx (Trial Assigning Individualized Options for Treatment) trial includes women with node-negative, HR-positive/HER2-negative tumors measuring 0.6 to 5 cm. All patients were treated with standard-of-care endocrine therapy for at least 5 years. Chemotherapy was determined based on the 21-gene recurrence score results on the primary tumor. The 21-gene recurrence score cutoffs were changed to low (0–10), intermediate (11–25), and high (≥ 26). Patients with scores of 26 or higher were treated with chemotherapy, and those with intermediate scores were randomly assigned to chemotherapy or no chemotherapy; results from this cohort are still pending. However, excellent breast cancer outcomes with endocrine therapy alone were reported from the 1626 (15.9% of total cohort) prospectively followed patients with low recurrence score tumors. The 5-year invasive disease-free survival was 93.8%, with overall survival of 98%.²⁸ Given that 5 years is appropriate follow-up to see any chemotherapy benefit, this data supports the recommendation for no chemotherapy in this cohort of patients with very low 21-gene recurrence scores.

The RxPONDER (Rx for Positive Node, Endocrine Responsive Breast Cancer) trial is evaluating women with 1 to 3 node-positive, HR-positive, HER2-negative tumors. In this trial, patients with 21-gene recurrence scores of 0 to 25 were assigned to adjuvant chemotherapy or none. Those with scores of 26 or higher were assigned to chemotherapy. All patients received standard adjuvant endocrine therapy. This study has completed accrual and results are pending. Of note, TAILORx and RxPONDER did not investigate the potential lack of benefit of endocrine therapy in cancers with high recurrence scores. Furthermore, despite data suggesting that chemotherapy may not even benefit women with 4 or more nodes involved but who have a low recurrence score,²⁴ due to the lack of prospective data in this cohort and the quite high risk for distant recurrence, chemotherapy continues to be the standard of care for these patients.

PAM50 (Breast Cancer Prognostic Gene Signature)

Using microarray and quantitative reverse transcriptase PCR (RT-PCR) on formalin-fixed paraffin-embedded (FFPE) tissues, the Breast Cancer Prognostic Gene Signature (PAM50) assay was initially developed to identify intrinsic breast cancer subtypes, including luminal A, luminal B, HER2-enriched, and basal-like.^7,29 Based on the prediction analysis of microarray (PAM) method, the assay measures the expression levels of 50 genes, provides a risk category (low, intermediate, and high), and generates a numerical risk of recurrence score (ROR). The intrinsic subtype and ROR have been shown to add significant prognostic value to the clinicopathological characteristics of tumors. Clinical validity of PAM50 was evaluated in postmenopausal women with HR-positive early-stage breast cancer treated in the prospective ATAC and ABCSG-8 (Austrian Breast and Colorectal Cancer Study Group 8) trials.^30,31 In 1017 patients with ER-positive breast cancer treated with anastrozole or tamoxifen in the ATAC trial, ROR added significant prognostic information beyond the clinical treatment score (integrated prognostic information from nodal status, tumor size, histopathologic grade, age, and anastrozole or tamoxifen treatment) in all patients. Also, compared with the 21-gene recurrence score, ROR provided more prognostic information in ER-positive, node-negative disease and better differentiation of intermediate- and higher-risk groups. Fewer patients were categorized as intermediate risk by ROR and more as high risk, which could reduce the uncertainty in the estimate of clinical benefit from chemotherapy.³⁰ The clinical utility of PAM50 as a prognostic model was also validated in 1478 postmenopausal women with ER-positive early-stage breast cancer enrolled in the ABCSG-8 trial. In this study, ROR assigned 47% of patients with node-negative disease to the low-risk category. In this low-risk group, the 10-year metastasis risk was less than 3.5%, indicating lack of benefit from additional chemotherapy.³¹ A key limitation of the PAM50 is the lack of any prospective studies with this assay.

PAM50 has been designed to be carried out in any qualified pathology laboratory. Moreover, the ROR score provides additional prognostic information about risk of late recurrence, which will be discussed in the next section.

70-Gene Breast Cancer Recurrence Assay (MammaPrint)

MammaPrint is a 70-gene assay that was initially developed using an unsupervised, hierarchical clustering algorithm on whole-genome expression arrays with early-stage breast cancer. Among 295 consecutive patients who had MammaPrint testing, those classified with a good-prognosis tumor signature (n = 115) had an excellent 10-year survival rate (94.5%) compared to those with a poor-prognosis signature (54.5%), and the signature remained prognostic upon multivariate analysis.³² Subsequently, a pooled analysis comparing outcomes by MammaPrint score in patients with node-negative or 1 to 3 node-positive breast cancers treated as per discretion of their medical team with either adjuvant chemotherapy plus endocrine therapy or endocrine therapy alone reported that only those patients with a high-risk score benefited from chemotherapy.³³ Recently, a prospective phase 3 study (MINDACT [Microarray In Node negative Disease may Avoid ChemoTherapy]) evaluating the utility of MammaPrint for adjuvant chemotherapy decision-making reported results.³⁴ In this study, 6693 women with early-stage breast cancer were assessed by clinical risk and genomic risk using MammaPrint. Those with low clinical and genomic risk did not receive chemotherapy, while those with high clinical and genomic risk all received chemotherapy. The primary goal of the study was to assess whether forgoing chemotherapy would be associated with a low rate of recurrence in those patients with a low-risk prognostic MammaPrint signature but high clinical risk. A total of 1550 patients (23.2%) were in the discordant group, and the majority of these patients had HR-positive disease (98.1%). Without chemotherapy, the rate of survival without distant metastasis at 5 years in this group was 94.7% (95% confidence interval [CI] 92.5% to 96.2%), which met the primary endpoint. Of note, initially, MammaPrint was only available for fresh tissue analysis, but recent advances in RNA processing now allow for this analysis on FFPE tissue.³⁵

Summary

These genomic and biomarker assays can identify different subsets of HR-positive breast cancers, including those patients who have tumors with an excellent prognosis with endocrine therapies alone. Thus, we now have the tools to help avoid the toxicities of chemotherapy in many women with early-stage breast cancer.

Tests for Assessing Risk for Late Recurrence

Case Continued

The patient undergoes 21-gene recurrence score testing, which shows a low recurrence score of 10, estimating the 10-year risk of distant recurrence to be approximately 7% with 5 years of tamoxifen. Chemotherapy is not recommended. The patient completes adjuvant whole breast radiation therapy, and then, based on data supporting AIs over tamoxifen in postmenopausal women, she is started on anastrozole.⁴¹ She initially experiences mild side effects from treatment, including fatigue, arthralgia, and vaginal dryness, but her symptoms are able to be managed. As she approaches 5 years of adjuvant endocrine therapy with anastrozole, she is struggling with rotator cuff injury and is anxious about recurrence, but has no evidence of recurrent cancer. Her bone density scan in the beginning of her fourth year of therapy shows a decrease in bone mineral density, with the lowest T score of –1.5 at the left femoral neck, consistent with osteopenia. She has been treated with calcium and vitamin D supplements.

• How long should this patient continue treatment with anastrozole?

The risk for recurrence is highest during the first 5 years after diagnosis for all patients with early breast cancer.⁴² Although HR-positive breast cancers have a better prognosis than HR-negative disease, the pattern of recurrence is different between the 2 groups, and it is estimated that approximately half of the recurrences among patients with HR-positive early breast cancer occur after the first 5 years from diagnosis. Annualized hazard of recurrence in HR-positive breast cancer has been shown to remain elevated and fairly stable beyond 10 years, even for those with low tumor burden and node-negative disease.⁴³ Prospective trials showed that for women with HR-positive early breast cancer, 5 years of adjuvant tamoxifen could substantially reduce recurrence rates and improve survival, and this became the standard of care.⁴⁴ AIs are considered the standard of care for adjuvant endocrine therapy in most postmenopausal women, as they result in a significantly lower recurrence rate compared with tamoxifen, either as initial adjuvant therapy or sequentially following 2 to 3 years of tamoxifen.⁴⁵

Due to the risk for later recurrences with HR-positive breast cancer, more patients and oncologists are considering extended endocrine therapy. This is based on results from the ATLAS (Adjuvant Tamoxifen: Longer Against Shorter) and aTTOM (Adjuvant Tamoxifen–To Offer More?) studies, both of which showed that women with HR-positive breast cancer who continued tamoxifen for 10 years had a lower late recurrence rate and a lower breast cancer mortality rate compared with those who stopped at 5 years.^46,47 Furthermore, the NCIC MA.17 trial evaluated extended endocrine therapy in postmenopausal women with 5 years of letrozole following 5 years of tamoxifen. Letrozole was shown to improve both disease-free and distant disease-free survival. The overall survival benefit was limited to patients with node-positive disease.⁴⁸ A summary of studies of extended endocrine therapy for HR-positive breast cancers is shown in Table 2.^2,3,46–49

However, extending AI therapy from 5 years to 10 years is not clearly beneficial. In the MA.17R trial, although longer AI therapy resulted in significantly better disease-free survival (95% versus 91%, hazard ratio 0.66, P = 0.01), this was primarily due to a lower incidence of contralateral breast cancer in those taking the AI compared with placebo. The distant recurrence risks were similar and low (4.4% versus 5.5%), and there was no overall survival difference.² Also, the NSABP B-42 study, which was presented at the 2016 San Antonio Breast Cancer Symposium, did not meet its predefined endpoint for benefit from extending adjuvant AI therapy with letrozole beyond 5 years.³ Thus, the absolute benefit from extended endocrine therapy has been modest across these studies. Although endocrine therapy is considered relatively safe and well tolerated, side effects can be significant and even associated with morbidity. Ideally, extended endocrine therapy should be offered to the subset of patients who would benefit the most. Several genomic diagnostic assays, including the EndoPredict test, PAM50, and the Breast Cancer Index (BCI) tests, specifically assess the risk for late recurrence in HR-positive cancers.

PAM50

Studies suggest that the ROR score also has value in predicting late recurrences. Analysis of data in patients enrolled in the ABCSG-8 trial showed that ROR could identify patients with endocrine-sensitive disease who are at low risk for late relapse and could be spared from unwanted toxicities of extended endocrine therapies. In 1246 ABCSG-8 patients between years 5 and 15, the PAM50 ROR demonstrated an absolute risk of distant recurrence of 2.4% in the low-risk group, as compared with 17.5% in the high-risk group.⁵⁰ Also, a combined analysis of patients from both the ATAC and ABCSG-8 trials demonstrated the utility of ROR in identifying this subgroup of patients with low risk for late relapse.⁵¹

EndoPredict

EndoPredict is another quantitative RT-PCR–based assay which uses FFPE tissues to calculate a risk score based on 8 cancer-related and 3 reference genes. The score is combined with clinicopathological factors including tumor size and nodal status to make a comprehensive risk score (EPclin). EPclin is used to dichotomize patients into EndoPredict low- and high-risk groups. EndoPredict has been validated in 2 cohorts of patients enrolled in separate randomized studies, ABCSG-6 and ABCSG-8. EP provided prognostic information beyond clinicopathological variables to predict distant recurrence in patients with HR-positive/HER2-negative early breast cancer.³⁷ More important, EndoPredict has been shown to predict early (years 0–5) versus late (> 5 years after diagnosis) recurrences and identify a low-risk subset of patients who would not be expected to benefit from further treatment beyond 5 years of endocrine therapy.⁵² Recently, EndoPredict and EPclin were compared with the 21-gene (Oncotype DX) recurrence score in a patient population from the TransATAC study. Both EndoPredict and EPclin provided more prognostic information compared to the 21-gene recurrence score and identified early and late relapse events.⁵³ EndoPredict is the first multigene expression assay that could be routinely performed in decentralized molecular pathological laboratories with a short turnaround time.⁵⁴

Breast Cancer Index

The BCI is a RT-PCR–based gene expression assay that consists of 2 gene expression biomarkers: molecular grade index (MGI) and HOXB13/IL17BR (H/I). The BCI was developed as a prognostic test to assess risk for breast cancer recurrence using a cohort of ER-positive patients (n = 588) treated with adjuvant tamoxifen versus observation from the prospective randomized Stockholm trial.³⁸ In this blinded retrospective study, H/I and MGI were measured and a continuous risk model (BCI) was developed in the tamoxifen-treated group. More than 50% of the patients in this group were classified as having a low risk of recurrence. The rate of distant recurrence or death in this low-risk group at 10 years was less than 3%. The performance of the BCI model was then tested in the untreated arm of the Stockholm trial. In the untreated arm, BCI classified 53%, 27%, and 20% of patients as low, intermediate, and high risk, respectively. The rate of distant metastasis at 10 years in these risk groups was 8.3% (95% CI 4.7% to 14.4%), 22.9% (95% CI 14.5% to 35.2%), and 28.5% (95% CI 17.9% to 43.6%), respectively, and the rate of breast cancer–specific mortality was 5.1% (95% CI 1.3% to 8.7%), 19.8% (95% CI 10.0% to 28.6%), and 28.8% (95% CI 15.3% to 40.2%).³⁸

The prognostic and predictive values of the BCI have been validated in other large, randomized studies and in patients with both node-negative and node-positive disease.^39,55 The predictive value of the endocrine-response biomarker, the H/I ratio, has been demonstrated in randomized studies. In the MA.17 trial, a high H/I ratio was associated with increased risk for late recurrence in the absence of letrozole. However, extended endocrine therapy with letrozole in patients with high H/I ratios predicted benefit from therapy and decreased the probability of late disease recurrence.⁵⁶ BCI was also compared to IHC4 and the 21-gene recurrence score in the TransATAC study and was the only test to show prognostic significance for both early (0–5 years) and late (5–10 year) recurrence.⁴⁰

The impact of the BCI results on physicians’ recommendations for extended endocrine therapy was assessed by a prospective study. This study showed that the test result had a significant effect on both physician treatment recommendation and patient satisfaction. BCI testing resulted in a change in physician recommendations for extended endocrine therapy, with an overall decrease in recommendations for extended endocrine therapy from 74% to 54%. Knowledge of the test result also led to improved patient satisfaction and decreased anxiety.⁵⁷

Summary

Due to the risk for late recurrence, extended endocrine therapy is being recommended for many patients with HR-positive breast cancers. Multiple genomic assays are being developed to better understand an individual’s risk for late recurrence and the potential for benefit from extended endocrine therapies. However, none of the assays has been validated in prospective randomized studies. Further validation is needed prior to routine use of these assays.

Case Continued

A BCI test is done and the result shows 4.3% BCI low-risk category in years 5–10, which is consistent with a low likelihood of benefit from extended endocrine therapy. After discussing the results of the BCI test in the context of no survival benefit from extending AIs beyond 5 years, both the patient and her oncologist feel comfortable with discontinuing endocrine therapy at the end of 5 years.

Conclusion

Reduction in breast cancer mortality is mainly the result of improved systemic treatments. With advances in breast cancer screening tools in recent years, the rate of cancer detection has increased. This has raised concerns regarding overdiagnosis. To prevent unwanted toxicities associated with overtreatment, better treatment decision tools are needed. Several genomic assays are currently available and widely used to provide prognostic and predictive information and aid in decisions regarding appropriate use of adjuvant chemotherapy in HR-positive/HER2-negative early-stage breast cancer. Ongoing studies are refining the cutoffs for these assays and expanding the applicability to node-positive breast cancers. Furthermore, with several studies now showing benefit from the use of extended endocrine therapy, some of these assays may be able to identify the subset of patients who are at increased risk for late recurrence and who might benefit from extended endocrine therapy. Advances in molecular testing has enabled clinicians to offer more personalized treatments to their patients, improve patients’ compliance, and decrease anxiety and conflict associated with management decisions. Although small numbers of patients with HER2-positive and triple-negative breast cancers were also included in some of these studies, use of genomic assays in this subset of patients is very limited and currently not recommended.

Introduction

Over the past several decades, while the incidence of breast cancer has increased, breast cancer mortality has decreased. This decrease is likely due to both early detection and advances in systemic therapy. However, with more widespread use of screening mammography, there are increasing concerns about potential overdiagnosis of cancer.¹ One key challenge is that breast cancer is a heterogeneous disease. Improved tools for determining breast cancer biology can help physicians individualize treatments. Patients with low-risk cancers can be approached with less aggressive treatments, thus preventing unnecessary toxicities, while those with higher-risk cancers remain treated appropriately with more aggressive therapies.

Traditionally, adjuvant chemotherapy was recommended based on tumor features such as stage (tumor size, regional nodal involvement), grade, expression of hormone receptors (estrogen receptor [ER] and progesterone receptor [PR]) and human epidermal growth factor receptor-2 (HER2), and patient features (age, menopausal status). However, this approach is not accurate enough to guide individualized treatment approaches, which are based on the risk for recurrence and the reduction in this risk that can be achieved with various systemic treatments. In particular, women with low-risk hormone receptor (HR)–positive, HER2-negative breast cancers could be spared the toxicities of cytotoxic chemotherapies without compromising the prognosis.

Beyond chemotherapy, endocrine therapies also have risks, especially when given over extended periods of time. Recently, extended endocrine therapy has been shown to prevent late recurrences of HR-positive breast cancers. In the National Cancer Institute of Canada Clinical Trials Group’s MA.17R study, extended endocrine therapy with letrozole for a total of 10 years (beyond 5 years of an aromatase inhibitor [AI]) decreased the risk for breast cancer recurrence or the occurrence of contralateral breast cancer by 34%.² However, the overall survival was similar between the 2 groups and the disease-free survival benefits were not confirmed in other studies.^3–5 Identifying the subgroup of patients who benefit from this extended AI therapy is important in the era of personalized medicine. Several tumor genomic assays have been developed to provide additional prognostic and predictive information with the goal of individualizing adjuvant therapies for breast cancer. Although assays are also being evaluated in HER2-positive and triple-negative breast cancer, this review will focus on HR-positive, HER2-negative breast cancer.

Tests for Guiding Adjuvant Chemotherapy Decisions

Case Study

Initial Presentation

A 54-year-old postmenopausal woman with no significant past medical history presents with an abnormal screening mammogram, which shows a focal asymmetry in the 10 o’clock position at middle depth of the left breast. Further work-up with a diagnostic mammogram and ultrasound of the left breast shows a suspicious hypoechoic solid mass with irregular margins measuring 17 mm. The patient undergoes an ultrasound-guided core needle biopsy of the suspicious mass, the results of which are consistent with an invasive ductal carcinoma, Nottingham grade 2, ER strongly positive (95%), PR weakly positive (5%), HER2-negative, and Ki-67 of 15%. She undergoes a left partial mastectomy and sentinel lymph node biopsy, with final pathology demonstrating a single focus of invasive ductal carcinoma, measuring 2.2 cm in greatest dimension with no evidence of lymphovascular invasion. Margins are clear and 2 sentinel lymph nodes are negative for metastatic disease (final pathologic stage IIA, pT2 pN0 cM0). She is referred to medical oncology to discuss adjuvant systemic therapy.

• Can additional testing be used to determine prognosis and guide systemic therapy recommendations for early-stage HR-positive/HER2-negative breast cancer?

After a diagnosis of early-stage breast cancer, the key clinical question faced by the patient and medical oncologist is: what is the individual’s risk for a metastatic breast cancer recurrence and thus the risk for death due to breast cancer? Once the risk for recurrence is established, systemic adjuvant chemotherapy, endocrine therapy, and/or HER2-directed therapy are considered based on the receptor status (ER/PR and HER2) to reduce this risk. HR-positive, HER2-negative breast cancer is the most common type of breast cancer. Although adjuvant endocrine therapy has significantly reduced the risk for recurrence and improved survival for patients with HR-positive breast cancer,⁶ the role of adjuvant chemotherapy for this subset of breast cancer remains unclear. Prior to genomic testing, the recommendation for adjuvant chemotherapy for HR-positive/HER2-negative tumors was primarily based on patient age and tumor stage and grade. However, chemotherapy overtreatment remained a concern given the potential short- and long-term risks of chemotherapy. Further studies into HR-positive/HER2-negative tumors have shown that these tumors can be divided into 2 main subtypes, luminal A and luminal B.⁷ These subtypes represent unique biology and differ in terms of prognosis and response to endocrine therapy and chemotherapy. Luminal A tumors are strongly endocrine responsive and have a good prognosis, while luminal B tumors are less endocrine responsive and are associated with a poorer prognosis; the addition of adjuvant chemotherapy is often considered for luminal B tumors.⁸ Several tests, including tumor genomic assays, are now available to help with delineating the tumor subtype and aid in decision-making regarding adjuvant chemotherapy for HR-positive/HER2-negative breast cancers.

Ki-67 Assays, Including IHC4 and PEPI

Proliferation is a hallmark of cancer cells.⁹ Ki-67, a nuclear nonhistone protein whose expression varies in intensity throughout the cell cycle, has been used as a measurement of tumor cell proliferation.¹⁰ Two large meta-analyses have demonstrated that high Ki-67 expression in breast tumors is independently associated with worse disease-free and overall survival rates.^11,12 Ki-67 expression has also been used to classify HR-positive tumors as luminal A or B. After classifying tumor subtypes based on intrinsic gene expression profiling, Cheang and colleagues determined that a Ki-67 cut point of 13.25% differentiated luminal A and B tumors.¹³ However, the ideal cut point for Ki-67 remains unclear, as the sensitivity and specificity in this study was 77% and 78%, respectively. Others have combined Ki-67 with standard ER, PR, and HER2 testing. This immunohistochemical 4 (IHC4) score, which weighs each of these variables, was validated in postmenopausal patients from the ATAC (Arimidex, Tamoxifen, Alone or in Combination) trial who had ER-positive tumors and did not receive chemotherapy.¹⁴ The prognostic information from the IHC4 was similar to that seen with the 21-gene recurrence score (Oncotype DX), which is discussed later in this article. The key challenge with Ki-67 testing currently is the lack of a validated test methodology and intra-observer variability in interpreting the Ki-67 results.¹⁵ Recent series have suggested that Ki-67 be considered as a continuous marker rather than a set cut point.¹⁶ These issues continue to impact the clinical utility of Ki-67 for decision-making for adjuvant chemotherapy.

Ki-67 and the preoperative endocrine prognostic index (PEPI) score have been explored in the neoadjuvant setting to separate postmenopausal women with endocrine-sensitive versus intrinsically resistant disease and identify patients at risk for recurrent disease.¹⁷ The on-treatment levels of Ki-67 in response to endocrine therapy have been shown to be more prognostic than baseline values, and a decrease in Ki-67 as early as 2 weeks after initiation of neoadjuvant endocrine therapy is associated with endocrine-sensitive tumors and improved outcome. The PEPI score was developed through retrospective analysis of the P024 trial¹⁸ to evaluate the relationship between post-neoadjuvant endocrine therapy tumor characteristics and risk for early relapse. The score was subsequently validated in an independent data set from the IMPACT (Immediate Preoperative Anastrozole, Tamoxifen, or Combined with Tamoxifen) trial.¹⁹ Patients with low pathological stage (0 or 1) and a favorable biomarker profile (PEPI score 0) at surgery had the best prognosis in the absence of chemotherapy. On the other hand, higher pathological stage at surgery and a poor biomarker profile with loss of ER positivity or persistently elevated Ki-67 (PEPI score of 3) identified de novo endocrine-resistant tumors that are higher risk for early relapse.²⁰ The ongoing Alliance A011106 ALTERNATE trial (ALTernate approaches for clinical stage II or III Estrogen Receptor positive breast cancer NeoAdjuvant TrEatment in postmenopausal women, NCT01953588) is a phase 3 study to prospectively test this hypothesis.

21-Gene Recurrence Score (Onco type DX Assay)

The 21-gene Oncotype DX assay is conducted on paraffin-embedded tumor tissue and measures the expression of 16 cancer related genes and 5 reference genes using quantitative polymerase chain reaction (PCR). The genes included in this assay are mainly related to proliferation (including Ki-67), invasion, and HER2 or estrogen signaling.²¹ Originally, the 21-gene recurrence score assay was analyzed as a prognostic biomarker tool in a prospective-retrospective biomarker substudy of the National Surgical Adjuvant Breast and Bowel Project (NSABP) B-14 clinical trial in which patients with node-negative, ER-positive tumors were randomly assigned to receive tamoxifen or placebo without chemotherapy.²² Using the standard reported values of low risk (< 18), intermediate risk (18–30), or high risk (≥ 31) for recurrence, among the tamoxifen-treated patients, cancers with a high-risk recurrence score had a significantly worse rate of distant recurrence and overall survival.²¹ Inferior breast cancer survival in cancers with a high recurrence score was also confirmed in other series of endocrine-treated patients with node-negative and node-positive disease.^23–25

The predictive utility of the 21-gene recurrence score for endocrine therapy has also been evaluated. A comparison of the placebo- and tamoxifen-treated patients from the NSABP B-14 trial demonstrated that the 21-gene recurrence score predicted benefit from tamoxifen in cancers with low- or intermediate-risk recurrence scores.²⁶ However, there was no benefit from the use of tamoxifen over placebo in cancers with high-risk recurrence scores. To date, this intriguing data has not been prospectively confirmed, and thus the 21-gene recurrence score is not used to avoid endocrine therapy.

The 21-gene recurrence score is primarily used by oncologists to aid in decision-making regarding adjuvant chemotherapy in patients with node-negative and node-positive (with up to 3 positive lymph nodes), HR-positive/HER2-negative breast cancers. The predictive utility of the 21-gene recurrence score for adjuvant chemotherapy was initially tested using tumor samples from the NSABP B-20 study. This study initially compared adjuvant tamoxifen alone with tamoxifen plus chemotherapy in patients with node-negative, HR-positive tumors. The prospective-retrospective biomarker analysis showed that the patients with high-risk 21-gene recurrence scores benefited from the addition of chemotherapy, whereas those with low or intermediate risk did not have an improved freedom from distant recurrence with chemotherapy.²⁷ Similarly, an analysis from the prospective phase 3 Southwest Oncology Group (SWOG) 8814 trial comparing tamoxifen to tamoxifen with chemotherapy showed that for node-positive tumors, chemotherapy benefit was only seen in those with high 21-gene recurrence scores.²⁴

Prospective studies are now starting to report results regarding the predictive role of the 21-gene recurrence score. The TAILORx (Trial Assigning Individualized Options for Treatment) trial includes women with node-negative, HR-positive/HER2-negative tumors measuring 0.6 to 5 cm. All patients were treated with standard-of-care endocrine therapy for at least 5 years. Chemotherapy was determined based on the 21-gene recurrence score results on the primary tumor. The 21-gene recurrence score cutoffs were changed to low (0–10), intermediate (11–25), and high (≥ 26). Patients with scores of 26 or higher were treated with chemotherapy, and those with intermediate scores were randomly assigned to chemotherapy or no chemotherapy; results from this cohort are still pending. However, excellent breast cancer outcomes with endocrine therapy alone were reported from the 1626 (15.9% of total cohort) prospectively followed patients with low recurrence score tumors. The 5-year invasive disease-free survival was 93.8%, with overall survival of 98%.²⁸ Given that 5 years is appropriate follow-up to see any chemotherapy benefit, this data supports the recommendation for no chemotherapy in this cohort of patients with very low 21-gene recurrence scores.

The RxPONDER (Rx for Positive Node, Endocrine Responsive Breast Cancer) trial is evaluating women with 1 to 3 node-positive, HR-positive, HER2-negative tumors. In this trial, patients with 21-gene recurrence scores of 0 to 25 were assigned to adjuvant chemotherapy or none. Those with scores of 26 or higher were assigned to chemotherapy. All patients received standard adjuvant endocrine therapy. This study has completed accrual and results are pending. Of note, TAILORx and RxPONDER did not investigate the potential lack of benefit of endocrine therapy in cancers with high recurrence scores. Furthermore, despite data suggesting that chemotherapy may not even benefit women with 4 or more nodes involved but who have a low recurrence score,²⁴ due to the lack of prospective data in this cohort and the quite high risk for distant recurrence, chemotherapy continues to be the standard of care for these patients.

PAM50 (Breast Cancer Prognostic Gene Signature)

Using microarray and quantitative reverse transcriptase PCR (RT-PCR) on formalin-fixed paraffin-embedded (FFPE) tissues, the Breast Cancer Prognostic Gene Signature (PAM50) assay was initially developed to identify intrinsic breast cancer subtypes, including luminal A, luminal B, HER2-enriched, and basal-like.^7,29 Based on the prediction analysis of microarray (PAM) method, the assay measures the expression levels of 50 genes, provides a risk category (low, intermediate, and high), and generates a numerical risk of recurrence score (ROR). The intrinsic subtype and ROR have been shown to add significant prognostic value to the clinicopathological characteristics of tumors. Clinical validity of PAM50 was evaluated in postmenopausal women with HR-positive early-stage breast cancer treated in the prospective ATAC and ABCSG-8 (Austrian Breast and Colorectal Cancer Study Group 8) trials.^30,31 In 1017 patients with ER-positive breast cancer treated with anastrozole or tamoxifen in the ATAC trial, ROR added significant prognostic information beyond the clinical treatment score (integrated prognostic information from nodal status, tumor size, histopathologic grade, age, and anastrozole or tamoxifen treatment) in all patients. Also, compared with the 21-gene recurrence score, ROR provided more prognostic information in ER-positive, node-negative disease and better differentiation of intermediate- and higher-risk groups. Fewer patients were categorized as intermediate risk by ROR and more as high risk, which could reduce the uncertainty in the estimate of clinical benefit from chemotherapy.³⁰ The clinical utility of PAM50 as a prognostic model was also validated in 1478 postmenopausal women with ER-positive early-stage breast cancer enrolled in the ABCSG-8 trial. In this study, ROR assigned 47% of patients with node-negative disease to the low-risk category. In this low-risk group, the 10-year metastasis risk was less than 3.5%, indicating lack of benefit from additional chemotherapy.³¹ A key limitation of the PAM50 is the lack of any prospective studies with this assay.

PAM50 has been designed to be carried out in any qualified pathology laboratory. Moreover, the ROR score provides additional prognostic information about risk of late recurrence, which will be discussed in the next section.

70-Gene Breast Cancer Recurrence Assay (MammaPrint)

MammaPrint is a 70-gene assay that was initially developed using an unsupervised, hierarchical clustering algorithm on whole-genome expression arrays with early-stage breast cancer. Among 295 consecutive patients who had MammaPrint testing, those classified with a good-prognosis tumor signature (n = 115) had an excellent 10-year survival rate (94.5%) compared to those with a poor-prognosis signature (54.5%), and the signature remained prognostic upon multivariate analysis.³² Subsequently, a pooled analysis comparing outcomes by MammaPrint score in patients with node-negative or 1 to 3 node-positive breast cancers treated as per discretion of their medical team with either adjuvant chemotherapy plus endocrine therapy or endocrine therapy alone reported that only those patients with a high-risk score benefited from chemotherapy.³³ Recently, a prospective phase 3 study (MINDACT [Microarray In Node negative Disease may Avoid ChemoTherapy]) evaluating the utility of MammaPrint for adjuvant chemotherapy decision-making reported results.³⁴ In this study, 6693 women with early-stage breast cancer were assessed by clinical risk and genomic risk using MammaPrint. Those with low clinical and genomic risk did not receive chemotherapy, while those with high clinical and genomic risk all received chemotherapy. The primary goal of the study was to assess whether forgoing chemotherapy would be associated with a low rate of recurrence in those patients with a low-risk prognostic MammaPrint signature but high clinical risk. A total of 1550 patients (23.2%) were in the discordant group, and the majority of these patients had HR-positive disease (98.1%). Without chemotherapy, the rate of survival without distant metastasis at 5 years in this group was 94.7% (95% confidence interval [CI] 92.5% to 96.2%), which met the primary endpoint. Of note, initially, MammaPrint was only available for fresh tissue analysis, but recent advances in RNA processing now allow for this analysis on FFPE tissue.³⁵

Summary

These genomic and biomarker assays can identify different subsets of HR-positive breast cancers, including those patients who have tumors with an excellent prognosis with endocrine therapies alone. Thus, we now have the tools to help avoid the toxicities of chemotherapy in many women with early-stage breast cancer.

Tests for Assessing Risk for Late Recurrence

Case Continued

The patient undergoes 21-gene recurrence score testing, which shows a low recurrence score of 10, estimating the 10-year risk of distant recurrence to be approximately 7% with 5 years of tamoxifen. Chemotherapy is not recommended. The patient completes adjuvant whole breast radiation therapy, and then, based on data supporting AIs over tamoxifen in postmenopausal women, she is started on anastrozole.⁴¹ She initially experiences mild side effects from treatment, including fatigue, arthralgia, and vaginal dryness, but her symptoms are able to be managed. As she approaches 5 years of adjuvant endocrine therapy with anastrozole, she is struggling with rotator cuff injury and is anxious about recurrence, but has no evidence of recurrent cancer. Her bone density scan in the beginning of her fourth year of therapy shows a decrease in bone mineral density, with the lowest T score of –1.5 at the left femoral neck, consistent with osteopenia. She has been treated with calcium and vitamin D supplements.

• How long should this patient continue treatment with anastrozole?

The risk for recurrence is highest during the first 5 years after diagnosis for all patients with early breast cancer.⁴² Although HR-positive breast cancers have a better prognosis than HR-negative disease, the pattern of recurrence is different between the 2 groups, and it is estimated that approximately half of the recurrences among patients with HR-positive early breast cancer occur after the first 5 years from diagnosis. Annualized hazard of recurrence in HR-positive breast cancer has been shown to remain elevated and fairly stable beyond 10 years, even for those with low tumor burden and node-negative disease.⁴³ Prospective trials showed that for women with HR-positive early breast cancer, 5 years of adjuvant tamoxifen could substantially reduce recurrence rates and improve survival, and this became the standard of care.⁴⁴ AIs are considered the standard of care for adjuvant endocrine therapy in most postmenopausal women, as they result in a significantly lower recurrence rate compared with tamoxifen, either as initial adjuvant therapy or sequentially following 2 to 3 years of tamoxifen.⁴⁵

Due to the risk for later recurrences with HR-positive breast cancer, more patients and oncologists are considering extended endocrine therapy. This is based on results from the ATLAS (Adjuvant Tamoxifen: Longer Against Shorter) and aTTOM (Adjuvant Tamoxifen–To Offer More?) studies, both of which showed that women with HR-positive breast cancer who continued tamoxifen for 10 years had a lower late recurrence rate and a lower breast cancer mortality rate compared with those who stopped at 5 years.^46,47 Furthermore, the NCIC MA.17 trial evaluated extended endocrine therapy in postmenopausal women with 5 years of letrozole following 5 years of tamoxifen. Letrozole was shown to improve both disease-free and distant disease-free survival. The overall survival benefit was limited to patients with node-positive disease.⁴⁸ A summary of studies of extended endocrine therapy for HR-positive breast cancers is shown in Table 2.^2,3,46–49

However, extending AI therapy from 5 years to 10 years is not clearly beneficial. In the MA.17R trial, although longer AI therapy resulted in significantly better disease-free survival (95% versus 91%, hazard ratio 0.66, P = 0.01), this was primarily due to a lower incidence of contralateral breast cancer in those taking the AI compared with placebo. The distant recurrence risks were similar and low (4.4% versus 5.5%), and there was no overall survival difference.² Also, the NSABP B-42 study, which was presented at the 2016 San Antonio Breast Cancer Symposium, did not meet its predefined endpoint for benefit from extending adjuvant AI therapy with letrozole beyond 5 years.³ Thus, the absolute benefit from extended endocrine therapy has been modest across these studies. Although endocrine therapy is considered relatively safe and well tolerated, side effects can be significant and even associated with morbidity. Ideally, extended endocrine therapy should be offered to the subset of patients who would benefit the most. Several genomic diagnostic assays, including the EndoPredict test, PAM50, and the Breast Cancer Index (BCI) tests, specifically assess the risk for late recurrence in HR-positive cancers.

PAM50

Studies suggest that the ROR score also has value in predicting late recurrences. Analysis of data in patients enrolled in the ABCSG-8 trial showed that ROR could identify patients with endocrine-sensitive disease who are at low risk for late relapse and could be spared from unwanted toxicities of extended endocrine therapies. In 1246 ABCSG-8 patients between years 5 and 15, the PAM50 ROR demonstrated an absolute risk of distant recurrence of 2.4% in the low-risk group, as compared with 17.5% in the high-risk group.⁵⁰ Also, a combined analysis of patients from both the ATAC and ABCSG-8 trials demonstrated the utility of ROR in identifying this subgroup of patients with low risk for late relapse.⁵¹

EndoPredict

EndoPredict is another quantitative RT-PCR–based assay which uses FFPE tissues to calculate a risk score based on 8 cancer-related and 3 reference genes. The score is combined with clinicopathological factors including tumor size and nodal status to make a comprehensive risk score (EPclin). EPclin is used to dichotomize patients into EndoPredict low- and high-risk groups. EndoPredict has been validated in 2 cohorts of patients enrolled in separate randomized studies, ABCSG-6 and ABCSG-8. EP provided prognostic information beyond clinicopathological variables to predict distant recurrence in patients with HR-positive/HER2-negative early breast cancer.³⁷ More important, EndoPredict has been shown to predict early (years 0–5) versus late (> 5 years after diagnosis) recurrences and identify a low-risk subset of patients who would not be expected to benefit from further treatment beyond 5 years of endocrine therapy.⁵² Recently, EndoPredict and EPclin were compared with the 21-gene (Oncotype DX) recurrence score in a patient population from the TransATAC study. Both EndoPredict and EPclin provided more prognostic information compared to the 21-gene recurrence score and identified early and late relapse events.⁵³ EndoPredict is the first multigene expression assay that could be routinely performed in decentralized molecular pathological laboratories with a short turnaround time.⁵⁴

Breast Cancer Index

The BCI is a RT-PCR–based gene expression assay that consists of 2 gene expression biomarkers: molecular grade index (MGI) and HOXB13/IL17BR (H/I). The BCI was developed as a prognostic test to assess risk for breast cancer recurrence using a cohort of ER-positive patients (n = 588) treated with adjuvant tamoxifen versus observation from the prospective randomized Stockholm trial.³⁸ In this blinded retrospective study, H/I and MGI were measured and a continuous risk model (BCI) was developed in the tamoxifen-treated group. More than 50% of the patients in this group were classified as having a low risk of recurrence. The rate of distant recurrence or death in this low-risk group at 10 years was less than 3%. The performance of the BCI model was then tested in the untreated arm of the Stockholm trial. In the untreated arm, BCI classified 53%, 27%, and 20% of patients as low, intermediate, and high risk, respectively. The rate of distant metastasis at 10 years in these risk groups was 8.3% (95% CI 4.7% to 14.4%), 22.9% (95% CI 14.5% to 35.2%), and 28.5% (95% CI 17.9% to 43.6%), respectively, and the rate of breast cancer–specific mortality was 5.1% (95% CI 1.3% to 8.7%), 19.8% (95% CI 10.0% to 28.6%), and 28.8% (95% CI 15.3% to 40.2%).³⁸

The prognostic and predictive values of the BCI have been validated in other large, randomized studies and in patients with both node-negative and node-positive disease.^39,55 The predictive value of the endocrine-response biomarker, the H/I ratio, has been demonstrated in randomized studies. In the MA.17 trial, a high H/I ratio was associated with increased risk for late recurrence in the absence of letrozole. However, extended endocrine therapy with letrozole in patients with high H/I ratios predicted benefit from therapy and decreased the probability of late disease recurrence.⁵⁶ BCI was also compared to IHC4 and the 21-gene recurrence score in the TransATAC study and was the only test to show prognostic significance for both early (0–5 years) and late (5–10 year) recurrence.⁴⁰

The impact of the BCI results on physicians’ recommendations for extended endocrine therapy was assessed by a prospective study. This study showed that the test result had a significant effect on both physician treatment recommendation and patient satisfaction. BCI testing resulted in a change in physician recommendations for extended endocrine therapy, with an overall decrease in recommendations for extended endocrine therapy from 74% to 54%. Knowledge of the test result also led to improved patient satisfaction and decreased anxiety.⁵⁷

Summary

Due to the risk for late recurrence, extended endocrine therapy is being recommended for many patients with HR-positive breast cancers. Multiple genomic assays are being developed to better understand an individual’s risk for late recurrence and the potential for benefit from extended endocrine therapies. However, none of the assays has been validated in prospective randomized studies. Further validation is needed prior to routine use of these assays.

Case Continued

A BCI test is done and the result shows 4.3% BCI low-risk category in years 5–10, which is consistent with a low likelihood of benefit from extended endocrine therapy. After discussing the results of the BCI test in the context of no survival benefit from extending AIs beyond 5 years, both the patient and her oncologist feel comfortable with discontinuing endocrine therapy at the end of 5 years.

Conclusion

Reduction in breast cancer mortality is mainly the result of improved systemic treatments. With advances in breast cancer screening tools in recent years, the rate of cancer detection has increased. This has raised concerns regarding overdiagnosis. To prevent unwanted toxicities associated with overtreatment, better treatment decision tools are needed. Several genomic assays are currently available and widely used to provide prognostic and predictive information and aid in decisions regarding appropriate use of adjuvant chemotherapy in HR-positive/HER2-negative early-stage breast cancer. Ongoing studies are refining the cutoffs for these assays and expanding the applicability to node-positive breast cancers. Furthermore, with several studies now showing benefit from the use of extended endocrine therapy, some of these assays may be able to identify the subset of patients who are at increased risk for late recurrence and who might benefit from extended endocrine therapy. Advances in molecular testing has enabled clinicians to offer more personalized treatments to their patients, improve patients’ compliance, and decrease anxiety and conflict associated with management decisions. Although small numbers of patients with HER2-positive and triple-negative breast cancers were also included in some of these studies, use of genomic assays in this subset of patients is very limited and currently not recommended.

Introduction

Over the past several decades, while the incidence of breast cancer has increased, breast cancer mortality has decreased. This decrease is likely due to both early detection and advances in systemic therapy. However, with more widespread use of screening mammography, there are increasing concerns about potential overdiagnosis of cancer.¹ One key challenge is that breast cancer is a heterogeneous disease. Improved tools for determining breast cancer biology can help physicians individualize treatments. Patients with low-risk cancers can be approached with less aggressive treatments, thus preventing unnecessary toxicities, while those with higher-risk cancers remain treated appropriately with more aggressive therapies.

Traditionally, adjuvant chemotherapy was recommended based on tumor features such as stage (tumor size, regional nodal involvement), grade, expression of hormone receptors (estrogen receptor [ER] and progesterone receptor [PR]) and human epidermal growth factor receptor-2 (HER2), and patient features (age, menopausal status). However, this approach is not accurate enough to guide individualized treatment approaches, which are based on the risk for recurrence and the reduction in this risk that can be achieved with various systemic treatments. In particular, women with low-risk hormone receptor (HR)–positive, HER2-negative breast cancers could be spared the toxicities of cytotoxic chemotherapies without compromising the prognosis.

Beyond chemotherapy, endocrine therapies also have risks, especially when given over extended periods of time. Recently, extended endocrine therapy has been shown to prevent late recurrences of HR-positive breast cancers. In the National Cancer Institute of Canada Clinical Trials Group’s MA.17R study, extended endocrine therapy with letrozole for a total of 10 years (beyond 5 years of an aromatase inhibitor [AI]) decreased the risk for breast cancer recurrence or the occurrence of contralateral breast cancer by 34%.² However, the overall survival was similar between the 2 groups and the disease-free survival benefits were not confirmed in other studies.^3–5 Identifying the subgroup of patients who benefit from this extended AI therapy is important in the era of personalized medicine. Several tumor genomic assays have been developed to provide additional prognostic and predictive information with the goal of individualizing adjuvant therapies for breast cancer. Although assays are also being evaluated in HER2-positive and triple-negative breast cancer, this review will focus on HR-positive, HER2-negative breast cancer.

Tests for Guiding Adjuvant Chemotherapy Decisions

Case Study

Initial Presentation

A 54-year-old postmenopausal woman with no significant past medical history presents with an abnormal screening mammogram, which shows a focal asymmetry in the 10 o’clock position at middle depth of the left breast. Further work-up with a diagnostic mammogram and ultrasound of the left breast shows a suspicious hypoechoic solid mass with irregular margins measuring 17 mm. The patient undergoes an ultrasound-guided core needle biopsy of the suspicious mass, the results of which are consistent with an invasive ductal carcinoma, Nottingham grade 2, ER strongly positive (95%), PR weakly positive (5%), HER2-negative, and Ki-67 of 15%. She undergoes a left partial mastectomy and sentinel lymph node biopsy, with final pathology demonstrating a single focus of invasive ductal carcinoma, measuring 2.2 cm in greatest dimension with no evidence of lymphovascular invasion. Margins are clear and 2 sentinel lymph nodes are negative for metastatic disease (final pathologic stage IIA, pT2 pN0 cM0). She is referred to medical oncology to discuss adjuvant systemic therapy.

• Can additional testing be used to determine prognosis and guide systemic therapy recommendations for early-stage HR-positive/HER2-negative breast cancer?

After a diagnosis of early-stage breast cancer, the key clinical question faced by the patient and medical oncologist is: what is the individual’s risk for a metastatic breast cancer recurrence and thus the risk for death due to breast cancer? Once the risk for recurrence is established, systemic adjuvant chemotherapy, endocrine therapy, and/or HER2-directed therapy are considered based on the receptor status (ER/PR and HER2) to reduce this risk. HR-positive, HER2-negative breast cancer is the most common type of breast cancer. Although adjuvant endocrine therapy has significantly reduced the risk for recurrence and improved survival for patients with HR-positive breast cancer,⁶ the role of adjuvant chemotherapy for this subset of breast cancer remains unclear. Prior to genomic testing, the recommendation for adjuvant chemotherapy for HR-positive/HER2-negative tumors was primarily based on patient age and tumor stage and grade. However, chemotherapy overtreatment remained a concern given the potential short- and long-term risks of chemotherapy. Further studies into HR-positive/HER2-negative tumors have shown that these tumors can be divided into 2 main subtypes, luminal A and luminal B.⁷ These subtypes represent unique biology and differ in terms of prognosis and response to endocrine therapy and chemotherapy. Luminal A tumors are strongly endocrine responsive and have a good prognosis, while luminal B tumors are less endocrine responsive and are associated with a poorer prognosis; the addition of adjuvant chemotherapy is often considered for luminal B tumors.⁸ Several tests, including tumor genomic assays, are now available to help with delineating the tumor subtype and aid in decision-making regarding adjuvant chemotherapy for HR-positive/HER2-negative breast cancers.

Ki-67 Assays, Including IHC4 and PEPI

Proliferation is a hallmark of cancer cells.⁹ Ki-67, a nuclear nonhistone protein whose expression varies in intensity throughout the cell cycle, has been used as a measurement of tumor cell proliferation.¹⁰ Two large meta-analyses have demonstrated that high Ki-67 expression in breast tumors is independently associated with worse disease-free and overall survival rates.^11,12 Ki-67 expression has also been used to classify HR-positive tumors as luminal A or B. After classifying tumor subtypes based on intrinsic gene expression profiling, Cheang and colleagues determined that a Ki-67 cut point of 13.25% differentiated luminal A and B tumors.¹³ However, the ideal cut point for Ki-67 remains unclear, as the sensitivity and specificity in this study was 77% and 78%, respectively. Others have combined Ki-67 with standard ER, PR, and HER2 testing. This immunohistochemical 4 (IHC4) score, which weighs each of these variables, was validated in postmenopausal patients from the ATAC (Arimidex, Tamoxifen, Alone or in Combination) trial who had ER-positive tumors and did not receive chemotherapy.¹⁴ The prognostic information from the IHC4 was similar to that seen with the 21-gene recurrence score (Oncotype DX), which is discussed later in this article. The key challenge with Ki-67 testing currently is the lack of a validated test methodology and intra-observer variability in interpreting the Ki-67 results.¹⁵ Recent series have suggested that Ki-67 be considered as a continuous marker rather than a set cut point.¹⁶ These issues continue to impact the clinical utility of Ki-67 for decision-making for adjuvant chemotherapy.

Ki-67 and the preoperative endocrine prognostic index (PEPI) score have been explored in the neoadjuvant setting to separate postmenopausal women with endocrine-sensitive versus intrinsically resistant disease and identify patients at risk for recurrent disease.¹⁷ The on-treatment levels of Ki-67 in response to endocrine therapy have been shown to be more prognostic than baseline values, and a decrease in Ki-67 as early as 2 weeks after initiation of neoadjuvant endocrine therapy is associated with endocrine-sensitive tumors and improved outcome. The PEPI score was developed through retrospective analysis of the P024 trial¹⁸ to evaluate the relationship between post-neoadjuvant endocrine therapy tumor characteristics and risk for early relapse. The score was subsequently validated in an independent data set from the IMPACT (Immediate Preoperative Anastrozole, Tamoxifen, or Combined with Tamoxifen) trial.¹⁹ Patients with low pathological stage (0 or 1) and a favorable biomarker profile (PEPI score 0) at surgery had the best prognosis in the absence of chemotherapy. On the other hand, higher pathological stage at surgery and a poor biomarker profile with loss of ER positivity or persistently elevated Ki-67 (PEPI score of 3) identified de novo endocrine-resistant tumors that are higher risk for early relapse.²⁰ The ongoing Alliance A011106 ALTERNATE trial (ALTernate approaches for clinical stage II or III Estrogen Receptor positive breast cancer NeoAdjuvant TrEatment in postmenopausal women, NCT01953588) is a phase 3 study to prospectively test this hypothesis.

21-Gene Recurrence Score (Onco type DX Assay)

The 21-gene Oncotype DX assay is conducted on paraffin-embedded tumor tissue and measures the expression of 16 cancer related genes and 5 reference genes using quantitative polymerase chain reaction (PCR). The genes included in this assay are mainly related to proliferation (including Ki-67), invasion, and HER2 or estrogen signaling.²¹ Originally, the 21-gene recurrence score assay was analyzed as a prognostic biomarker tool in a prospective-retrospective biomarker substudy of the National Surgical Adjuvant Breast and Bowel Project (NSABP) B-14 clinical trial in which patients with node-negative, ER-positive tumors were randomly assigned to receive tamoxifen or placebo without chemotherapy.²² Using the standard reported values of low risk (< 18), intermediate risk (18–30), or high risk (≥ 31) for recurrence, among the tamoxifen-treated patients, cancers with a high-risk recurrence score had a significantly worse rate of distant recurrence and overall survival.²¹ Inferior breast cancer survival in cancers with a high recurrence score was also confirmed in other series of endocrine-treated patients with node-negative and node-positive disease.^23–25

The predictive utility of the 21-gene recurrence score for endocrine therapy has also been evaluated. A comparison of the placebo- and tamoxifen-treated patients from the NSABP B-14 trial demonstrated that the 21-gene recurrence score predicted benefit from tamoxifen in cancers with low- or intermediate-risk recurrence scores.²⁶ However, there was no benefit from the use of tamoxifen over placebo in cancers with high-risk recurrence scores. To date, this intriguing data has not been prospectively confirmed, and thus the 21-gene recurrence score is not used to avoid endocrine therapy.

The 21-gene recurrence score is primarily used by oncologists to aid in decision-making regarding adjuvant chemotherapy in patients with node-negative and node-positive (with up to 3 positive lymph nodes), HR-positive/HER2-negative breast cancers. The predictive utility of the 21-gene recurrence score for adjuvant chemotherapy was initially tested using tumor samples from the NSABP B-20 study. This study initially compared adjuvant tamoxifen alone with tamoxifen plus chemotherapy in patients with node-negative, HR-positive tumors. The prospective-retrospective biomarker analysis showed that the patients with high-risk 21-gene recurrence scores benefited from the addition of chemotherapy, whereas those with low or intermediate risk did not have an improved freedom from distant recurrence with chemotherapy.²⁷ Similarly, an analysis from the prospective phase 3 Southwest Oncology Group (SWOG) 8814 trial comparing tamoxifen to tamoxifen with chemotherapy showed that for node-positive tumors, chemotherapy benefit was only seen in those with high 21-gene recurrence scores.²⁴

Prospective studies are now starting to report results regarding the predictive role of the 21-gene recurrence score. The TAILORx (Trial Assigning Individualized Options for Treatment) trial includes women with node-negative, HR-positive/HER2-negative tumors measuring 0.6 to 5 cm. All patients were treated with standard-of-care endocrine therapy for at least 5 years. Chemotherapy was determined based on the 21-gene recurrence score results on the primary tumor. The 21-gene recurrence score cutoffs were changed to low (0–10), intermediate (11–25), and high (≥ 26). Patients with scores of 26 or higher were treated with chemotherapy, and those with intermediate scores were randomly assigned to chemotherapy or no chemotherapy; results from this cohort are still pending. However, excellent breast cancer outcomes with endocrine therapy alone were reported from the 1626 (15.9% of total cohort) prospectively followed patients with low recurrence score tumors. The 5-year invasive disease-free survival was 93.8%, with overall survival of 98%.²⁸ Given that 5 years is appropriate follow-up to see any chemotherapy benefit, this data supports the recommendation for no chemotherapy in this cohort of patients with very low 21-gene recurrence scores.

The RxPONDER (Rx for Positive Node, Endocrine Responsive Breast Cancer) trial is evaluating women with 1 to 3 node-positive, HR-positive, HER2-negative tumors. In this trial, patients with 21-gene recurrence scores of 0 to 25 were assigned to adjuvant chemotherapy or none. Those with scores of 26 or higher were assigned to chemotherapy. All patients received standard adjuvant endocrine therapy. This study has completed accrual and results are pending. Of note, TAILORx and RxPONDER did not investigate the potential lack of benefit of endocrine therapy in cancers with high recurrence scores. Furthermore, despite data suggesting that chemotherapy may not even benefit women with 4 or more nodes involved but who have a low recurrence score,²⁴ due to the lack of prospective data in this cohort and the quite high risk for distant recurrence, chemotherapy continues to be the standard of care for these patients.

PAM50 (Breast Cancer Prognostic Gene Signature)

Using microarray and quantitative reverse transcriptase PCR (RT-PCR) on formalin-fixed paraffin-embedded (FFPE) tissues, the Breast Cancer Prognostic Gene Signature (PAM50) assay was initially developed to identify intrinsic breast cancer subtypes, including luminal A, luminal B, HER2-enriched, and basal-like.^7,29 Based on the prediction analysis of microarray (PAM) method, the assay measures the expression levels of 50 genes, provides a risk category (low, intermediate, and high), and generates a numerical risk of recurrence score (ROR). The intrinsic subtype and ROR have been shown to add significant prognostic value to the clinicopathological characteristics of tumors. Clinical validity of PAM50 was evaluated in postmenopausal women with HR-positive early-stage breast cancer treated in the prospective ATAC and ABCSG-8 (Austrian Breast and Colorectal Cancer Study Group 8) trials.^30,31 In 1017 patients with ER-positive breast cancer treated with anastrozole or tamoxifen in the ATAC trial, ROR added significant prognostic information beyond the clinical treatment score (integrated prognostic information from nodal status, tumor size, histopathologic grade, age, and anastrozole or tamoxifen treatment) in all patients. Also, compared with the 21-gene recurrence score, ROR provided more prognostic information in ER-positive, node-negative disease and better differentiation of intermediate- and higher-risk groups. Fewer patients were categorized as intermediate risk by ROR and more as high risk, which could reduce the uncertainty in the estimate of clinical benefit from chemotherapy.³⁰ The clinical utility of PAM50 as a prognostic model was also validated in 1478 postmenopausal women with ER-positive early-stage breast cancer enrolled in the ABCSG-8 trial. In this study, ROR assigned 47% of patients with node-negative disease to the low-risk category. In this low-risk group, the 10-year metastasis risk was less than 3.5%, indicating lack of benefit from additional chemotherapy.³¹ A key limitation of the PAM50 is the lack of any prospective studies with this assay.

PAM50 has been designed to be carried out in any qualified pathology laboratory. Moreover, the ROR score provides additional prognostic information about risk of late recurrence, which will be discussed in the next section.

70-Gene Breast Cancer Recurrence Assay (MammaPrint)

MammaPrint is a 70-gene assay that was initially developed using an unsupervised, hierarchical clustering algorithm on whole-genome expression arrays with early-stage breast cancer. Among 295 consecutive patients who had MammaPrint testing, those classified with a good-prognosis tumor signature (n = 115) had an excellent 10-year survival rate (94.5%) compared to those with a poor-prognosis signature (54.5%), and the signature remained prognostic upon multivariate analysis.³² Subsequently, a pooled analysis comparing outcomes by MammaPrint score in patients with node-negative or 1 to 3 node-positive breast cancers treated as per discretion of their medical team with either adjuvant chemotherapy plus endocrine therapy or endocrine therapy alone reported that only those patients with a high-risk score benefited from chemotherapy.³³ Recently, a prospective phase 3 study (MINDACT [Microarray In Node negative Disease may Avoid ChemoTherapy]) evaluating the utility of MammaPrint for adjuvant chemotherapy decision-making reported results.³⁴ In this study, 6693 women with early-stage breast cancer were assessed by clinical risk and genomic risk using MammaPrint. Those with low clinical and genomic risk did not receive chemotherapy, while those with high clinical and genomic risk all received chemotherapy. The primary goal of the study was to assess whether forgoing chemotherapy would be associated with a low rate of recurrence in those patients with a low-risk prognostic MammaPrint signature but high clinical risk. A total of 1550 patients (23.2%) were in the discordant group, and the majority of these patients had HR-positive disease (98.1%). Without chemotherapy, the rate of survival without distant metastasis at 5 years in this group was 94.7% (95% confidence interval [CI] 92.5% to 96.2%), which met the primary endpoint. Of note, initially, MammaPrint was only available for fresh tissue analysis, but recent advances in RNA processing now allow for this analysis on FFPE tissue.³⁵

Summary

These genomic and biomarker assays can identify different subsets of HR-positive breast cancers, including those patients who have tumors with an excellent prognosis with endocrine therapies alone. Thus, we now have the tools to help avoid the toxicities of chemotherapy in many women with early-stage breast cancer.

Tests for Assessing Risk for Late Recurrence

Case Continued

The patient undergoes 21-gene recurrence score testing, which shows a low recurrence score of 10, estimating the 10-year risk of distant recurrence to be approximately 7% with 5 years of tamoxifen. Chemotherapy is not recommended. The patient completes adjuvant whole breast radiation therapy, and then, based on data supporting AIs over tamoxifen in postmenopausal women, she is started on anastrozole.⁴¹ She initially experiences mild side effects from treatment, including fatigue, arthralgia, and vaginal dryness, but her symptoms are able to be managed. As she approaches 5 years of adjuvant endocrine therapy with anastrozole, she is struggling with rotator cuff injury and is anxious about recurrence, but has no evidence of recurrent cancer. Her bone density scan in the beginning of her fourth year of therapy shows a decrease in bone mineral density, with the lowest T score of –1.5 at the left femoral neck, consistent with osteopenia. She has been treated with calcium and vitamin D supplements.

• How long should this patient continue treatment with anastrozole?

The risk for recurrence is highest during the first 5 years after diagnosis for all patients with early breast cancer.⁴² Although HR-positive breast cancers have a better prognosis than HR-negative disease, the pattern of recurrence is different between the 2 groups, and it is estimated that approximately half of the recurrences among patients with HR-positive early breast cancer occur after the first 5 years from diagnosis. Annualized hazard of recurrence in HR-positive breast cancer has been shown to remain elevated and fairly stable beyond 10 years, even for those with low tumor burden and node-negative disease.⁴³ Prospective trials showed that for women with HR-positive early breast cancer, 5 years of adjuvant tamoxifen could substantially reduce recurrence rates and improve survival, and this became the standard of care.⁴⁴ AIs are considered the standard of care for adjuvant endocrine therapy in most postmenopausal women, as they result in a significantly lower recurrence rate compared with tamoxifen, either as initial adjuvant therapy or sequentially following 2 to 3 years of tamoxifen.⁴⁵

Due to the risk for later recurrences with HR-positive breast cancer, more patients and oncologists are considering extended endocrine therapy. This is based on results from the ATLAS (Adjuvant Tamoxifen: Longer Against Shorter) and aTTOM (Adjuvant Tamoxifen–To Offer More?) studies, both of which showed that women with HR-positive breast cancer who continued tamoxifen for 10 years had a lower late recurrence rate and a lower breast cancer mortality rate compared with those who stopped at 5 years.^46,47 Furthermore, the NCIC MA.17 trial evaluated extended endocrine therapy in postmenopausal women with 5 years of letrozole following 5 years of tamoxifen. Letrozole was shown to improve both disease-free and distant disease-free survival. The overall survival benefit was limited to patients with node-positive disease.⁴⁸ A summary of studies of extended endocrine therapy for HR-positive breast cancers is shown in Table 2.^2,3,46–49

However, extending AI therapy from 5 years to 10 years is not clearly beneficial. In the MA.17R trial, although longer AI therapy resulted in significantly better disease-free survival (95% versus 91%, hazard ratio 0.66, P = 0.01), this was primarily due to a lower incidence of contralateral breast cancer in those taking the AI compared with placebo. The distant recurrence risks were similar and low (4.4% versus 5.5%), and there was no overall survival difference.² Also, the NSABP B-42 study, which was presented at the 2016 San Antonio Breast Cancer Symposium, did not meet its predefined endpoint for benefit from extending adjuvant AI therapy with letrozole beyond 5 years.³ Thus, the absolute benefit from extended endocrine therapy has been modest across these studies. Although endocrine therapy is considered relatively safe and well tolerated, side effects can be significant and even associated with morbidity. Ideally, extended endocrine therapy should be offered to the subset of patients who would benefit the most. Several genomic diagnostic assays, including the EndoPredict test, PAM50, and the Breast Cancer Index (BCI) tests, specifically assess the risk for late recurrence in HR-positive cancers.

PAM50

Studies suggest that the ROR score also has value in predicting late recurrences. Analysis of data in patients enrolled in the ABCSG-8 trial showed that ROR could identify patients with endocrine-sensitive disease who are at low risk for late relapse and could be spared from unwanted toxicities of extended endocrine therapies. In 1246 ABCSG-8 patients between years 5 and 15, the PAM50 ROR demonstrated an absolute risk of distant recurrence of 2.4% in the low-risk group, as compared with 17.5% in the high-risk group.⁵⁰ Also, a combined analysis of patients from both the ATAC and ABCSG-8 trials demonstrated the utility of ROR in identifying this subgroup of patients with low risk for late relapse.⁵¹

EndoPredict

EndoPredict is another quantitative RT-PCR–based assay which uses FFPE tissues to calculate a risk score based on 8 cancer-related and 3 reference genes. The score is combined with clinicopathological factors including tumor size and nodal status to make a comprehensive risk score (EPclin). EPclin is used to dichotomize patients into EndoPredict low- and high-risk groups. EndoPredict has been validated in 2 cohorts of patients enrolled in separate randomized studies, ABCSG-6 and ABCSG-8. EP provided prognostic information beyond clinicopathological variables to predict distant recurrence in patients with HR-positive/HER2-negative early breast cancer.³⁷ More important, EndoPredict has been shown to predict early (years 0–5) versus late (> 5 years after diagnosis) recurrences and identify a low-risk subset of patients who would not be expected to benefit from further treatment beyond 5 years of endocrine therapy.⁵² Recently, EndoPredict and EPclin were compared with the 21-gene (Oncotype DX) recurrence score in a patient population from the TransATAC study. Both EndoPredict and EPclin provided more prognostic information compared to the 21-gene recurrence score and identified early and late relapse events.⁵³ EndoPredict is the first multigene expression assay that could be routinely performed in decentralized molecular pathological laboratories with a short turnaround time.⁵⁴

Breast Cancer Index

The BCI is a RT-PCR–based gene expression assay that consists of 2 gene expression biomarkers: molecular grade index (MGI) and HOXB13/IL17BR (H/I). The BCI was developed as a prognostic test to assess risk for breast cancer recurrence using a cohort of ER-positive patients (n = 588) treated with adjuvant tamoxifen versus observation from the prospective randomized Stockholm trial.³⁸ In this blinded retrospective study, H/I and MGI were measured and a continuous risk model (BCI) was developed in the tamoxifen-treated group. More than 50% of the patients in this group were classified as having a low risk of recurrence. The rate of distant recurrence or death in this low-risk group at 10 years was less than 3%. The performance of the BCI model was then tested in the untreated arm of the Stockholm trial. In the untreated arm, BCI classified 53%, 27%, and 20% of patients as low, intermediate, and high risk, respectively. The rate of distant metastasis at 10 years in these risk groups was 8.3% (95% CI 4.7% to 14.4%), 22.9% (95% CI 14.5% to 35.2%), and 28.5% (95% CI 17.9% to 43.6%), respectively, and the rate of breast cancer–specific mortality was 5.1% (95% CI 1.3% to 8.7%), 19.8% (95% CI 10.0% to 28.6%), and 28.8% (95% CI 15.3% to 40.2%).³⁸

The prognostic and predictive values of the BCI have been validated in other large, randomized studies and in patients with both node-negative and node-positive disease.^39,55 The predictive value of the endocrine-response biomarker, the H/I ratio, has been demonstrated in randomized studies. In the MA.17 trial, a high H/I ratio was associated with increased risk for late recurrence in the absence of letrozole. However, extended endocrine therapy with letrozole in patients with high H/I ratios predicted benefit from therapy and decreased the probability of late disease recurrence.⁵⁶ BCI was also compared to IHC4 and the 21-gene recurrence score in the TransATAC study and was the only test to show prognostic significance for both early (0–5 years) and late (5–10 year) recurrence.⁴⁰

The impact of the BCI results on physicians’ recommendations for extended endocrine therapy was assessed by a prospective study. This study showed that the test result had a significant effect on both physician treatment recommendation and patient satisfaction. BCI testing resulted in a change in physician recommendations for extended endocrine therapy, with an overall decrease in recommendations for extended endocrine therapy from 74% to 54%. Knowledge of the test result also led to improved patient satisfaction and decreased anxiety.⁵⁷

Summary

Due to the risk for late recurrence, extended endocrine therapy is being recommended for many patients with HR-positive breast cancers. Multiple genomic assays are being developed to better understand an individual’s risk for late recurrence and the potential for benefit from extended endocrine therapies. However, none of the assays has been validated in prospective randomized studies. Further validation is needed prior to routine use of these assays.

Case Continued

A BCI test is done and the result shows 4.3% BCI low-risk category in years 5–10, which is consistent with a low likelihood of benefit from extended endocrine therapy. After discussing the results of the BCI test in the context of no survival benefit from extending AIs beyond 5 years, both the patient and her oncologist feel comfortable with discontinuing endocrine therapy at the end of 5 years.

Conclusion

Reduction in breast cancer mortality is mainly the result of improved systemic treatments. With advances in breast cancer screening tools in recent years, the rate of cancer detection has increased. This has raised concerns regarding overdiagnosis. To prevent unwanted toxicities associated with overtreatment, better treatment decision tools are needed. Several genomic assays are currently available and widely used to provide prognostic and predictive information and aid in decisions regarding appropriate use of adjuvant chemotherapy in HR-positive/HER2-negative early-stage breast cancer. Ongoing studies are refining the cutoffs for these assays and expanding the applicability to node-positive breast cancers. Furthermore, with several studies now showing benefit from the use of extended endocrine therapy, some of these assays may be able to identify the subset of patients who are at increased risk for late recurrence and who might benefit from extended endocrine therapy. Advances in molecular testing has enabled clinicians to offer more personalized treatments to their patients, improve patients’ compliance, and decrease anxiety and conflict associated with management decisions. Although small numbers of patients with HER2-positive and triple-negative breast cancers were also included in some of these studies, use of genomic assays in this subset of patients is very limited and currently not recommended.

Indian Health Service (IHS) has awarded grants worth $16.5 million to 4 behavioral health programs serving American Indians and Alaska Natives. The programs are Substance Abuse and Suicide Prevention (SASP), the Domestic Violence Prevention Program (DVPP), the Behavioral Health Integration Initiative (BH21), and Preventing Alcohol-Related Deaths (PARD).

Related: Development and Implementation of a Homeless Mobile Medical/Mental Veteran Intervention

Substance Abuse and Suicide Prevention provides culturally appropriate prevention and early intervention strategies aimed at reducing suicide and substance use and misuse among Native youth. Projects implement evidence-based, practice-based, and emerging practices to build resiliency, foster positive development, and promote family engagement.

The DVPP funding will expand outreach and increase awareness of domestic and sexual violence, provide victim advocacy, intervention, case coordination, policy development, community response teams, community and school education programs, and forensic health care services.

Related: New Center of Excellence to Lead Research of “Signature Wounds”

The BH21 is a new funding opportunity at IHS. It assists awardees in planning, developing, implementing, and evaluating behavioral health integration with primary care.

Preventing Alcohol-Related Deaths also is a new program. Funding increases access to social detoxification, evaluation, stabilization, and fostering patient readiness for and entry into treatment.

Indian Health Service (IHS) has awarded grants worth $16.5 million to 4 behavioral health programs serving American Indians and Alaska Natives. The programs are Substance Abuse and Suicide Prevention (SASP), the Domestic Violence Prevention Program (DVPP), the Behavioral Health Integration Initiative (BH21), and Preventing Alcohol-Related Deaths (PARD).

Related: Development and Implementation of a Homeless Mobile Medical/Mental Veteran Intervention

Substance Abuse and Suicide Prevention provides culturally appropriate prevention and early intervention strategies aimed at reducing suicide and substance use and misuse among Native youth. Projects implement evidence-based, practice-based, and emerging practices to build resiliency, foster positive development, and promote family engagement.

The DVPP funding will expand outreach and increase awareness of domestic and sexual violence, provide victim advocacy, intervention, case coordination, policy development, community response teams, community and school education programs, and forensic health care services.

Related: New Center of Excellence to Lead Research of “Signature Wounds”

The BH21 is a new funding opportunity at IHS. It assists awardees in planning, developing, implementing, and evaluating behavioral health integration with primary care.

Preventing Alcohol-Related Deaths also is a new program. Funding increases access to social detoxification, evaluation, stabilization, and fostering patient readiness for and entry into treatment.

Indian Health Service (IHS) has awarded grants worth $16.5 million to 4 behavioral health programs serving American Indians and Alaska Natives. The programs are Substance Abuse and Suicide Prevention (SASP), the Domestic Violence Prevention Program (DVPP), the Behavioral Health Integration Initiative (BH21), and Preventing Alcohol-Related Deaths (PARD).

Related: Development and Implementation of a Homeless Mobile Medical/Mental Veteran Intervention

Substance Abuse and Suicide Prevention provides culturally appropriate prevention and early intervention strategies aimed at reducing suicide and substance use and misuse among Native youth. Projects implement evidence-based, practice-based, and emerging practices to build resiliency, foster positive development, and promote family engagement.

The DVPP funding will expand outreach and increase awareness of domestic and sexual violence, provide victim advocacy, intervention, case coordination, policy development, community response teams, community and school education programs, and forensic health care services.

Related: New Center of Excellence to Lead Research of “Signature Wounds”

The BH21 is a new funding opportunity at IHS. It assists awardees in planning, developing, implementing, and evaluating behavioral health integration with primary care.

Preventing Alcohol-Related Deaths also is a new program. Funding increases access to social detoxification, evaluation, stabilization, and fostering patient readiness for and entry into treatment.

Photo by Aaron Logan

Researchers say they have identified a multiple myeloma (MM)-specific target for chimeric antigen receptor (CAR) T-cell therapy.

The team unearthed an MM-specific monoclonal antibody (mAb) and designed a CAR that incorporates a fragment derived from that mAb.

The resulting CAR T-cell therapy exhibited anti-MM activity in vitro and in vivo but did not have a negative effect on normal hematopoietic cells.

The researchers described this work in Nature Medicine.

The team believed that new antigen epitopes could be discovered by thoroughly searching for cancer-specific mAbs and characterizing the antigens they recognize.

“We applied this strategy to identify novel therapeutic targets for multiple myeloma . . . ,” explained study author Naoki Hosen, MD, PhD, of Osaka University in Osaka, Japan.

The researchers screened more than 10,000 anti-MM mAb clones and identified MMG49 as an MM-specific mAb that recognizes a subset of integrin β7 molecules.

The team found that MMG49 reacted to MM cells—but not to normal hematopoietic cells—in MM patient samples.

This prompted the researchers to design a CAR that incorporates a fragment derived from MMG49.

When tested in vitro, MMG49 CAR T cells exhibited cytotoxic activity against cell lines expressing the MMG49 epitope and primary MM cell from patients’ bone marrow. However, MMG49 CAR T cells did not have cytotoxic effects on MMG49-negative cells or normal hematopoietic cells.

The researchers said MM cells were completely eradicated by MMG49 CAR T cells. But the therapy did not kill T cells, even when integrin β₇ was activated by MAdCAM-1 and CXCL12.

In mouse models of MM, MMG49 CAR T cells significantly prolonged survival when compared to a CD19 CAR T-cell therapy. MMG49 CAR T cells eradicated MM cells and significantly decreased tumor burden in some mice, but some mice relapsed.

MMG49 CAR T cells did not affect normal hematopoietic cells in the mice, and the researchers said there were no unexpected side effects with the treatment.

“Our results also demonstrate that the active conformer of integrin β7 can serve as an immunotherapeutic target against MM, even though the expression of the protein itself is not specific to MM,” said study author Yukiko Matsunaga, PhD, of Princess Margaret Cancer Centre, University Health Network, in Toronto, Canada.

“Therefore, it’s highly plausible that there are other cancer immunotherapeutic targets that have yet to be identified in many cell-surface proteins that undergo conformational changes, even if the expression of the proteins themselves is not cancer-specific.”

Photo by Aaron Logan

Researchers say they have identified a multiple myeloma (MM)-specific target for chimeric antigen receptor (CAR) T-cell therapy.

The team unearthed an MM-specific monoclonal antibody (mAb) and designed a CAR that incorporates a fragment derived from that mAb.

The resulting CAR T-cell therapy exhibited anti-MM activity in vitro and in vivo but did not have a negative effect on normal hematopoietic cells.

The researchers described this work in Nature Medicine.

The team believed that new antigen epitopes could be discovered by thoroughly searching for cancer-specific mAbs and characterizing the antigens they recognize.

“We applied this strategy to identify novel therapeutic targets for multiple myeloma . . . ,” explained study author Naoki Hosen, MD, PhD, of Osaka University in Osaka, Japan.

The researchers screened more than 10,000 anti-MM mAb clones and identified MMG49 as an MM-specific mAb that recognizes a subset of integrin β7 molecules.

The team found that MMG49 reacted to MM cells—but not to normal hematopoietic cells—in MM patient samples.

This prompted the researchers to design a CAR that incorporates a fragment derived from MMG49.

When tested in vitro, MMG49 CAR T cells exhibited cytotoxic activity against cell lines expressing the MMG49 epitope and primary MM cell from patients’ bone marrow. However, MMG49 CAR T cells did not have cytotoxic effects on MMG49-negative cells or normal hematopoietic cells.

The researchers said MM cells were completely eradicated by MMG49 CAR T cells. But the therapy did not kill T cells, even when integrin β₇ was activated by MAdCAM-1 and CXCL12.

In mouse models of MM, MMG49 CAR T cells significantly prolonged survival when compared to a CD19 CAR T-cell therapy. MMG49 CAR T cells eradicated MM cells and significantly decreased tumor burden in some mice, but some mice relapsed.

MMG49 CAR T cells did not affect normal hematopoietic cells in the mice, and the researchers said there were no unexpected side effects with the treatment.

“Our results also demonstrate that the active conformer of integrin β7 can serve as an immunotherapeutic target against MM, even though the expression of the protein itself is not specific to MM,” said study author Yukiko Matsunaga, PhD, of Princess Margaret Cancer Centre, University Health Network, in Toronto, Canada.

“Therefore, it’s highly plausible that there are other cancer immunotherapeutic targets that have yet to be identified in many cell-surface proteins that undergo conformational changes, even if the expression of the proteins themselves is not cancer-specific.”

Photo by Aaron Logan

Researchers say they have identified a multiple myeloma (MM)-specific target for chimeric antigen receptor (CAR) T-cell therapy.

The team unearthed an MM-specific monoclonal antibody (mAb) and designed a CAR that incorporates a fragment derived from that mAb.

The resulting CAR T-cell therapy exhibited anti-MM activity in vitro and in vivo but did not have a negative effect on normal hematopoietic cells.

The researchers described this work in Nature Medicine.

The team believed that new antigen epitopes could be discovered by thoroughly searching for cancer-specific mAbs and characterizing the antigens they recognize.

“We applied this strategy to identify novel therapeutic targets for multiple myeloma . . . ,” explained study author Naoki Hosen, MD, PhD, of Osaka University in Osaka, Japan.

The researchers screened more than 10,000 anti-MM mAb clones and identified MMG49 as an MM-specific mAb that recognizes a subset of integrin β7 molecules.

The team found that MMG49 reacted to MM cells—but not to normal hematopoietic cells—in MM patient samples.

This prompted the researchers to design a CAR that incorporates a fragment derived from MMG49.

When tested in vitro, MMG49 CAR T cells exhibited cytotoxic activity against cell lines expressing the MMG49 epitope and primary MM cell from patients’ bone marrow. However, MMG49 CAR T cells did not have cytotoxic effects on MMG49-negative cells or normal hematopoietic cells.

The researchers said MM cells were completely eradicated by MMG49 CAR T cells. But the therapy did not kill T cells, even when integrin β₇ was activated by MAdCAM-1 and CXCL12.

In mouse models of MM, MMG49 CAR T cells significantly prolonged survival when compared to a CD19 CAR T-cell therapy. MMG49 CAR T cells eradicated MM cells and significantly decreased tumor burden in some mice, but some mice relapsed.

MMG49 CAR T cells did not affect normal hematopoietic cells in the mice, and the researchers said there were no unexpected side effects with the treatment.

“Our results also demonstrate that the active conformer of integrin β7 can serve as an immunotherapeutic target against MM, even though the expression of the protein itself is not specific to MM,” said study author Yukiko Matsunaga, PhD, of Princess Margaret Cancer Centre, University Health Network, in Toronto, Canada.

“Therefore, it’s highly plausible that there are other cancer immunotherapeutic targets that have yet to be identified in many cell-surface proteins that undergo conformational changes, even if the expression of the proteins themselves is not cancer-specific.”

mycosis fungoides

The US Food and Drug Administration (FDA) has accepted for priority review the biologics license application (BLA) for mogamulizumab.

Mogamulizumab is a humanized monoclonal antibody directed against CCR4 that is being developed by Kyowa Hakko Kirin Co., Ltd.

The company is seeking FDA approval for mogamulizumab as a treatment for patients with cutaneous T-cell lymphoma (CTCL) who have received at least 1 prior systemic therapy.

The FDA expects to make a decision on the BLA by June 4, 2018.

The FDA’s goal is to take action on a priority review application within 6 months of receiving it, rather than the standard 10 months.

The FDA grants priority review to applications for products that may provide significant improvements in the treatment, diagnosis, or prevention of serious conditions.

The BLA for mogamulizumab is supported by data from the MAVORIC study, the largest global randomized clinical trial of systemic therapy in CTCL.

MAVORIC is a phase 3 trial in which researchers evaluated mogamulizumab and an active comparator in 372 patients with CTCL who had failed at least 1 prior systemic treatment. The study was conducted in the US, Europe, Japan, and Australia.

Results from this trial are scheduled to be presented at the 2017 ASH Annual Meeting (abstract 817).

The FDA previously granted mogamulizumab breakthrough therapy designation as a treatment for CTCL patients who have received at least 1 prior systemic therapy.

Breakthrough designation is intended to expedite the development and review of new treatments for serious or life-threatening conditions. The designation entitles the company developing a therapy to more intensive FDA guidance on an efficient and accelerated development program, as well as eligibility for other actions to expedite FDA review, such as rolling submission and priority review.

To earn breakthrough designation, a treatment must show encouraging early clinical results demonstrating substantial improvement over available therapies with regard to a clinically significant endpoint, or it must fulfill an unmet need.

mycosis fungoides

The US Food and Drug Administration (FDA) has accepted for priority review the biologics license application (BLA) for mogamulizumab.

Mogamulizumab is a humanized monoclonal antibody directed against CCR4 that is being developed by Kyowa Hakko Kirin Co., Ltd.

The company is seeking FDA approval for mogamulizumab as a treatment for patients with cutaneous T-cell lymphoma (CTCL) who have received at least 1 prior systemic therapy.

The FDA expects to make a decision on the BLA by June 4, 2018.

The FDA’s goal is to take action on a priority review application within 6 months of receiving it, rather than the standard 10 months.

The FDA grants priority review to applications for products that may provide significant improvements in the treatment, diagnosis, or prevention of serious conditions.

The BLA for mogamulizumab is supported by data from the MAVORIC study, the largest global randomized clinical trial of systemic therapy in CTCL.

MAVORIC is a phase 3 trial in which researchers evaluated mogamulizumab and an active comparator in 372 patients with CTCL who had failed at least 1 prior systemic treatment. The study was conducted in the US, Europe, Japan, and Australia.

Results from this trial are scheduled to be presented at the 2017 ASH Annual Meeting (abstract 817).

The FDA previously granted mogamulizumab breakthrough therapy designation as a treatment for CTCL patients who have received at least 1 prior systemic therapy.

Breakthrough designation is intended to expedite the development and review of new treatments for serious or life-threatening conditions. The designation entitles the company developing a therapy to more intensive FDA guidance on an efficient and accelerated development program, as well as eligibility for other actions to expedite FDA review, such as rolling submission and priority review.

To earn breakthrough designation, a treatment must show encouraging early clinical results demonstrating substantial improvement over available therapies with regard to a clinically significant endpoint, or it must fulfill an unmet need.

mycosis fungoides

The US Food and Drug Administration (FDA) has accepted for priority review the biologics license application (BLA) for mogamulizumab.

Mogamulizumab is a humanized monoclonal antibody directed against CCR4 that is being developed by Kyowa Hakko Kirin Co., Ltd.

The company is seeking FDA approval for mogamulizumab as a treatment for patients with cutaneous T-cell lymphoma (CTCL) who have received at least 1 prior systemic therapy.

The FDA expects to make a decision on the BLA by June 4, 2018.

The FDA’s goal is to take action on a priority review application within 6 months of receiving it, rather than the standard 10 months.

The FDA grants priority review to applications for products that may provide significant improvements in the treatment, diagnosis, or prevention of serious conditions.

The BLA for mogamulizumab is supported by data from the MAVORIC study, the largest global randomized clinical trial of systemic therapy in CTCL.

MAVORIC is a phase 3 trial in which researchers evaluated mogamulizumab and an active comparator in 372 patients with CTCL who had failed at least 1 prior systemic treatment. The study was conducted in the US, Europe, Japan, and Australia.

Results from this trial are scheduled to be presented at the 2017 ASH Annual Meeting (abstract 817).

The FDA previously granted mogamulizumab breakthrough therapy designation as a treatment for CTCL patients who have received at least 1 prior systemic therapy.

Breakthrough designation is intended to expedite the development and review of new treatments for serious or life-threatening conditions. The designation entitles the company developing a therapy to more intensive FDA guidance on an efficient and accelerated development program, as well as eligibility for other actions to expedite FDA review, such as rolling submission and priority review.

To earn breakthrough designation, a treatment must show encouraging early clinical results demonstrating substantial improvement over available therapies with regard to a clinically significant endpoint, or it must fulfill an unmet need.

Image from Graham Beards

The US Food and Drug Administration (FDA) has granted priority review to the new drug application (NDA) for avatrombopag.

Avatrombopag is a second-generation thrombopoietin receptor agonist that is intended to address the limitations of existing treatments for thrombocytopenia.

With this NDA, Dova Pharmaceuticals, Inc., is seeking approval of avatrombopag for the treatment of thrombocytopenia in patients with chronic liver disease who are scheduled to undergo a procedure.

The FDA expects to make a decision on the NDA by May 21, 2018.

The FDA’s goal is to take action on a priority review application within 6 months of receiving it, rather than the standard 10 months.

The FDA grants priority review to applications for products that may provide significant improvements in the treatment, diagnosis, or prevention of serious conditions.

Phase 3 trials

The NDA submission for avatrombopag is supported by 2 identically designed phase 3 trials, ADAPT 1 and ADAPT 2. Results from these trials were presented at the 2017 American Association for the Study of Liver Disease (AASLD) Meeting last month (abstract 217).

The studies randomized 435 patients with thrombocytopenia and chronic liver disease who were scheduled to undergo a procedure.

Patients with low baseline platelet counts (<40x 10⁹/L) were randomized to receive 60 mg of avatrombopag or placebo daily for 5 days.

Patients with higher baseline platelet counts (40 to <50 x 10⁹/L) were randomized to receive 40 mg of avatrombopag or placebo daily for 5 days.

Patients underwent their procedures 5 to 8 days after their last dose of avatrombopag.

In ADAPT-1, 85 patients completed treatment with avatrombopag at 60 mg, 55 completed treatment with avatrombopag at 40 mg, and 78 controls completed the study.

In ADAPT-2, 68 patients completed treatment with avatrombopag at 60 mg, 55 completed treatment with avatrombopag at 40 mg, and 68 controls completed the study.

Efficacy

The primary efficacy endpoint of these trials was the proportion of patients who did not require any bleeding rescue up to 7 days post-procedure. Bleeding rescue included platelet transfusion, fresh frozen plasma, cryoprecipitate, vitamin K (phytonadione), desmopressin, recombinant activated factor VII, aminocaproicacid, tranexamic acid, whole blood transfusion, packed red cell transfusion, surgical intervention, or interventional radiology.

In ADAPT-1, the primary endpoint was achieved by 66% of patients who received avatrombopag at 60 mg and 23% of those who received placebo in the low-platelet-count cohort (P<0.0001). The endpoint was also achieved by 88% of patients who received avatrombopag at 40 mg and 38% of controls in the higher-platelet-count cohort (P<0.0001).

In ADAPT-2, the primary endpoint was achieved by 69% of patients who received avatrombopag at 60 mg and 35% of those who received placebo in the low-platelet-count cohort (P<0.0006). The endpoint was also achieved by 88% of patients who received avatrombopag at 40 mg and 33% of controls in the higher- platelet-count cohort (P<0.0001).

A secondary efficacy endpoint was the proportion of patients achieving the target platelet count (≥50 x 10⁹/L).

In ADAPT-1, this endpoint was met by 69% of patients who received avatrombopag at 60 mg and 4% of controls in the low-platelet-count cohort (P<0.0001). It was also met by 88% of patients who received avatrombopag at 40 mg and 21% of controls in the higher-platelet-count cohort (P<0.0001)

In ADAPT-2, this endpoint was met by 67% of patients who received avatrombopag at 60 mg and 7% of controls in the low-platelet-count cohort (P<0.0001). It was also met by 93% of patients who received avatrombopag at 40 mg and 39% of controls in the higher-platelet-count cohort (P<0.0001).

Safety

The researchers pooled safety data from the 2 trials.

Treatment-emergent adverse events (AEs) occurred in 58.2% of controls and 56% of avatrombopag-treated patients in the low-platelet-count cohort (60 mg). Treatment-emergent AEs also occurred in 50.8% of controls and 51.3% of avatrombopag-treated patients in the higher-platelet-count cohort (40 mg).

The most frequently reported treatment-emergent AEs were pyrexia, abdominal pain, nausea, headache, diarrhea, and fatigue.

One patient experienced partial portal vein thrombosis that was considered non-serious and potentially related to avatrombopag.

Treatment-related AEs occurred in 17.6% of controls and 11.3% of avatrombopag-treated patients in the low-platelet-count cohort. Treatment-related AEs also occurred in 6.2% of controls and 7% of avatrombopag-treated patients in the higher-platelet-count cohort.

Serious AEs occurred in 13.2%, 6.9%, 3.1%, and 7.8%, respectively.

There were 3 deaths—2 in the 40 mg avatrombopag arm in ADAPT-1 and 1 in the control group in ADAPT-2. None of the deaths was considered treatment-related.

Future directions

Dova Pharmaceuticals, Inc., is planning to explore the potential use of avatrombopag in a broader population of patients with thrombocytopenia. This includes patients undergoing surgical procedures associated with a high risk of bleeding and patients who develop thrombocytopenia after receiving chemotherapy.

In addition, the company is exploring a potential regulatory approval pathway for avatrombopag for the treatment of adults with chronic immune thrombocytopenic purpura based on results from a completed phase 3 trial in this patient population.

Image from Graham Beards

The US Food and Drug Administration (FDA) has granted priority review to the new drug application (NDA) for avatrombopag.

Avatrombopag is a second-generation thrombopoietin receptor agonist that is intended to address the limitations of existing treatments for thrombocytopenia.

With this NDA, Dova Pharmaceuticals, Inc., is seeking approval of avatrombopag for the treatment of thrombocytopenia in patients with chronic liver disease who are scheduled to undergo a procedure.

The FDA expects to make a decision on the NDA by May 21, 2018.

The FDA’s goal is to take action on a priority review application within 6 months of receiving it, rather than the standard 10 months.

The FDA grants priority review to applications for products that may provide significant improvements in the treatment, diagnosis, or prevention of serious conditions.

Phase 3 trials

The NDA submission for avatrombopag is supported by 2 identically designed phase 3 trials, ADAPT 1 and ADAPT 2. Results from these trials were presented at the 2017 American Association for the Study of Liver Disease (AASLD) Meeting last month (abstract 217).

The studies randomized 435 patients with thrombocytopenia and chronic liver disease who were scheduled to undergo a procedure.

Patients with low baseline platelet counts (<40x 10⁹/L) were randomized to receive 60 mg of avatrombopag or placebo daily for 5 days.

Patients with higher baseline platelet counts (40 to <50 x 10⁹/L) were randomized to receive 40 mg of avatrombopag or placebo daily for 5 days.

Patients underwent their procedures 5 to 8 days after their last dose of avatrombopag.

In ADAPT-1, 85 patients completed treatment with avatrombopag at 60 mg, 55 completed treatment with avatrombopag at 40 mg, and 78 controls completed the study.

In ADAPT-2, 68 patients completed treatment with avatrombopag at 60 mg, 55 completed treatment with avatrombopag at 40 mg, and 68 controls completed the study.

Efficacy

The primary efficacy endpoint of these trials was the proportion of patients who did not require any bleeding rescue up to 7 days post-procedure. Bleeding rescue included platelet transfusion, fresh frozen plasma, cryoprecipitate, vitamin K (phytonadione), desmopressin, recombinant activated factor VII, aminocaproicacid, tranexamic acid, whole blood transfusion, packed red cell transfusion, surgical intervention, or interventional radiology.

In ADAPT-1, the primary endpoint was achieved by 66% of patients who received avatrombopag at 60 mg and 23% of those who received placebo in the low-platelet-count cohort (P<0.0001). The endpoint was also achieved by 88% of patients who received avatrombopag at 40 mg and 38% of controls in the higher-platelet-count cohort (P<0.0001).

In ADAPT-2, the primary endpoint was achieved by 69% of patients who received avatrombopag at 60 mg and 35% of those who received placebo in the low-platelet-count cohort (P<0.0006). The endpoint was also achieved by 88% of patients who received avatrombopag at 40 mg and 33% of controls in the higher- platelet-count cohort (P<0.0001).

A secondary efficacy endpoint was the proportion of patients achieving the target platelet count (≥50 x 10⁹/L).

In ADAPT-1, this endpoint was met by 69% of patients who received avatrombopag at 60 mg and 4% of controls in the low-platelet-count cohort (P<0.0001). It was also met by 88% of patients who received avatrombopag at 40 mg and 21% of controls in the higher-platelet-count cohort (P<0.0001)

In ADAPT-2, this endpoint was met by 67% of patients who received avatrombopag at 60 mg and 7% of controls in the low-platelet-count cohort (P<0.0001). It was also met by 93% of patients who received avatrombopag at 40 mg and 39% of controls in the higher-platelet-count cohort (P<0.0001).

Safety

The researchers pooled safety data from the 2 trials.

Treatment-emergent adverse events (AEs) occurred in 58.2% of controls and 56% of avatrombopag-treated patients in the low-platelet-count cohort (60 mg). Treatment-emergent AEs also occurred in 50.8% of controls and 51.3% of avatrombopag-treated patients in the higher-platelet-count cohort (40 mg).

The most frequently reported treatment-emergent AEs were pyrexia, abdominal pain, nausea, headache, diarrhea, and fatigue.

One patient experienced partial portal vein thrombosis that was considered non-serious and potentially related to avatrombopag.

Treatment-related AEs occurred in 17.6% of controls and 11.3% of avatrombopag-treated patients in the low-platelet-count cohort. Treatment-related AEs also occurred in 6.2% of controls and 7% of avatrombopag-treated patients in the higher-platelet-count cohort.

Serious AEs occurred in 13.2%, 6.9%, 3.1%, and 7.8%, respectively.

There were 3 deaths—2 in the 40 mg avatrombopag arm in ADAPT-1 and 1 in the control group in ADAPT-2. None of the deaths was considered treatment-related.

Future directions

Dova Pharmaceuticals, Inc., is planning to explore the potential use of avatrombopag in a broader population of patients with thrombocytopenia. This includes patients undergoing surgical procedures associated with a high risk of bleeding and patients who develop thrombocytopenia after receiving chemotherapy.

In addition, the company is exploring a potential regulatory approval pathway for avatrombopag for the treatment of adults with chronic immune thrombocytopenic purpura based on results from a completed phase 3 trial in this patient population.

Image from Graham Beards

The US Food and Drug Administration (FDA) has granted priority review to the new drug application (NDA) for avatrombopag.

Avatrombopag is a second-generation thrombopoietin receptor agonist that is intended to address the limitations of existing treatments for thrombocytopenia.

With this NDA, Dova Pharmaceuticals, Inc., is seeking approval of avatrombopag for the treatment of thrombocytopenia in patients with chronic liver disease who are scheduled to undergo a procedure.

The FDA expects to make a decision on the NDA by May 21, 2018.

The FDA’s goal is to take action on a priority review application within 6 months of receiving it, rather than the standard 10 months.

The FDA grants priority review to applications for products that may provide significant improvements in the treatment, diagnosis, or prevention of serious conditions.

Phase 3 trials

The NDA submission for avatrombopag is supported by 2 identically designed phase 3 trials, ADAPT 1 and ADAPT 2. Results from these trials were presented at the 2017 American Association for the Study of Liver Disease (AASLD) Meeting last month (abstract 217).

The studies randomized 435 patients with thrombocytopenia and chronic liver disease who were scheduled to undergo a procedure.

Patients with low baseline platelet counts (<40x 10⁹/L) were randomized to receive 60 mg of avatrombopag or placebo daily for 5 days.

Patients with higher baseline platelet counts (40 to <50 x 10⁹/L) were randomized to receive 40 mg of avatrombopag or placebo daily for 5 days.

Patients underwent their procedures 5 to 8 days after their last dose of avatrombopag.

In ADAPT-1, 85 patients completed treatment with avatrombopag at 60 mg, 55 completed treatment with avatrombopag at 40 mg, and 78 controls completed the study.

In ADAPT-2, 68 patients completed treatment with avatrombopag at 60 mg, 55 completed treatment with avatrombopag at 40 mg, and 68 controls completed the study.

Efficacy

The primary efficacy endpoint of these trials was the proportion of patients who did not require any bleeding rescue up to 7 days post-procedure. Bleeding rescue included platelet transfusion, fresh frozen plasma, cryoprecipitate, vitamin K (phytonadione), desmopressin, recombinant activated factor VII, aminocaproicacid, tranexamic acid, whole blood transfusion, packed red cell transfusion, surgical intervention, or interventional radiology.

In ADAPT-1, the primary endpoint was achieved by 66% of patients who received avatrombopag at 60 mg and 23% of those who received placebo in the low-platelet-count cohort (P<0.0001). The endpoint was also achieved by 88% of patients who received avatrombopag at 40 mg and 38% of controls in the higher-platelet-count cohort (P<0.0001).

In ADAPT-2, the primary endpoint was achieved by 69% of patients who received avatrombopag at 60 mg and 35% of those who received placebo in the low-platelet-count cohort (P<0.0006). The endpoint was also achieved by 88% of patients who received avatrombopag at 40 mg and 33% of controls in the higher- platelet-count cohort (P<0.0001).

A secondary efficacy endpoint was the proportion of patients achieving the target platelet count (≥50 x 10⁹/L).

In ADAPT-1, this endpoint was met by 69% of patients who received avatrombopag at 60 mg and 4% of controls in the low-platelet-count cohort (P<0.0001). It was also met by 88% of patients who received avatrombopag at 40 mg and 21% of controls in the higher-platelet-count cohort (P<0.0001)

In ADAPT-2, this endpoint was met by 67% of patients who received avatrombopag at 60 mg and 7% of controls in the low-platelet-count cohort (P<0.0001). It was also met by 93% of patients who received avatrombopag at 40 mg and 39% of controls in the higher-platelet-count cohort (P<0.0001).

Safety

The researchers pooled safety data from the 2 trials.

Treatment-emergent adverse events (AEs) occurred in 58.2% of controls and 56% of avatrombopag-treated patients in the low-platelet-count cohort (60 mg). Treatment-emergent AEs also occurred in 50.8% of controls and 51.3% of avatrombopag-treated patients in the higher-platelet-count cohort (40 mg).

The most frequently reported treatment-emergent AEs were pyrexia, abdominal pain, nausea, headache, diarrhea, and fatigue.

One patient experienced partial portal vein thrombosis that was considered non-serious and potentially related to avatrombopag.

Treatment-related AEs occurred in 17.6% of controls and 11.3% of avatrombopag-treated patients in the low-platelet-count cohort. Treatment-related AEs also occurred in 6.2% of controls and 7% of avatrombopag-treated patients in the higher-platelet-count cohort.

Serious AEs occurred in 13.2%, 6.9%, 3.1%, and 7.8%, respectively.

There were 3 deaths—2 in the 40 mg avatrombopag arm in ADAPT-1 and 1 in the control group in ADAPT-2. None of the deaths was considered treatment-related.

Future directions

Dova Pharmaceuticals, Inc., is planning to explore the potential use of avatrombopag in a broader population of patients with thrombocytopenia. This includes patients undergoing surgical procedures associated with a high risk of bleeding and patients who develop thrombocytopenia after receiving chemotherapy.

In addition, the company is exploring a potential regulatory approval pathway for avatrombopag for the treatment of adults with chronic immune thrombocytopenic purpura based on results from a completed phase 3 trial in this patient population.

PARIS – Young adults with treatment-resistant depression have more than double the risk of all-cause mortality, compared with their peers with major depressive disorder that’s not treatment resistant, Johan Reutfors, MD, PhD, reported at the annual congress of the European College of Neuropsychopharmacology.

Across the full age spectrum of adults with treatment-resistant depression, however, the magnitude of the increased risk associated with treatment-resistant depression is less extreme than in the 18- to 29-year-olds. Yet, the moderate overall 11% increased risk of all-cause mortality in adults with treatment-resistant depression, compared with those with non–treatment-resistant major depressive disorder remains both statistically significant and clinically meaningful, observed Dr. Reutfors, a psychiatrist at the Karolinska Institute in Stockholm.

Bruce Jancin/Frontline Medical News

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PARIS – Young adults with treatment-resistant depression have more than double the risk of all-cause mortality, compared with their peers with major depressive disorder that’s not treatment resistant, Johan Reutfors, MD, PhD, reported at the annual congress of the European College of Neuropsychopharmacology.

Across the full age spectrum of adults with treatment-resistant depression, however, the magnitude of the increased risk associated with treatment-resistant depression is less extreme than in the 18- to 29-year-olds. Yet, the moderate overall 11% increased risk of all-cause mortality in adults with treatment-resistant depression, compared with those with non–treatment-resistant major depressive disorder remains both statistically significant and clinically meaningful, observed Dr. Reutfors, a psychiatrist at the Karolinska Institute in Stockholm.

Bruce Jancin/Frontline Medical News

[email protected]

PARIS – Young adults with treatment-resistant depression have more than double the risk of all-cause mortality, compared with their peers with major depressive disorder that’s not treatment resistant, Johan Reutfors, MD, PhD, reported at the annual congress of the European College of Neuropsychopharmacology.

Across the full age spectrum of adults with treatment-resistant depression, however, the magnitude of the increased risk associated with treatment-resistant depression is less extreme than in the 18- to 29-year-olds. Yet, the moderate overall 11% increased risk of all-cause mortality in adults with treatment-resistant depression, compared with those with non–treatment-resistant major depressive disorder remains both statistically significant and clinically meaningful, observed Dr. Reutfors, a psychiatrist at the Karolinska Institute in Stockholm.

Bruce Jancin/Frontline Medical News

[email protected]

HIV diagnoses are coming sooner after infection, increasing physicians’ ability to treat and prevent the spread of HIV, according to a new Centers for Disease Control and Prevention (CDC) Vital Signs report.

As HIV testing has increased, the percentage of people aware of their HIV infection has also steadily grown. As of 2014, 85% of people living with HIV in the United States were aware of their infection. This knowledge allows individuals to seek antiretroviral treatment to suppress the virus, which decreases morbidity and mortality while reducing the risk of sexual transmission to others; knowing one’s HIV status, then, is incredibly important, clinicians say, because people who are unaware that they are HIV positive account for approximately 40% of ongoing transmissions.

grandeduc/Thinkstock

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HIV diagnoses are coming sooner after infection, increasing physicians’ ability to treat and prevent the spread of HIV, according to a new Centers for Disease Control and Prevention (CDC) Vital Signs report.

As HIV testing has increased, the percentage of people aware of their HIV infection has also steadily grown. As of 2014, 85% of people living with HIV in the United States were aware of their infection. This knowledge allows individuals to seek antiretroviral treatment to suppress the virus, which decreases morbidity and mortality while reducing the risk of sexual transmission to others; knowing one’s HIV status, then, is incredibly important, clinicians say, because people who are unaware that they are HIV positive account for approximately 40% of ongoing transmissions.

grandeduc/Thinkstock

[email protected]

HIV diagnoses are coming sooner after infection, increasing physicians’ ability to treat and prevent the spread of HIV, according to a new Centers for Disease Control and Prevention (CDC) Vital Signs report.

As HIV testing has increased, the percentage of people aware of their HIV infection has also steadily grown. As of 2014, 85% of people living with HIV in the United States were aware of their infection. This knowledge allows individuals to seek antiretroviral treatment to suppress the virus, which decreases morbidity and mortality while reducing the risk of sexual transmission to others; knowing one’s HIV status, then, is incredibly important, clinicians say, because people who are unaware that they are HIV positive account for approximately 40% of ongoing transmissions.

grandeduc/Thinkstock

[email protected]