Cleveland Clinic Journal of Medicine

Mary, age 38, was hospitalized for acute cholecystitis requiring laparoscopic surgery. Her hospital course was uneventful. At the time of discharge, I, her inpatient doctor, prescribed 15 hydrocodone tablets for postoperative pain. I never saw her again. Did she struggle to stop taking the hydrocodone I prescribed?

Heather is a 50-year-old patient in my addiction medicine clinic who developed opioid use disorder while being treated for chronic pain. After much hardship and to her credit, she is now in long-term remission. Did her opioid use disorder start with an opioid prescription for an accepted indication?

The issues Mary and Heather face seem unrelated, but these 2 patients may be at different time points in the progression of the same disease. As a hospitalist, I want to optimize the chances that patients taking opioids for acute pain will be able to stop taking them.

CHRONIC USE VS OPIOID USE DISORDER

There is a distinction between chronic use of opioids and opioid use disorder. The latter is also known as addiction.

Patients who take opioids daily do not necessarily have opioid use disorder, even if they have physiologic dependence on them. Physiologic opioid dependence is commonly confused with opioid use disorder, but it is the expected result of regularly taking these drugs.

Opioid use disorder is a chronic disease of the brain characterized by loss of control over opioid use, resulting in harm. The Diagnostic and Statistical Manual, fifth edition, excludes physiologic dependence on opioids (tolerance and withdrawal) from its criteria for opioid use disorder if the patient is taking opioids solely under medical supervision.¹ To be diagnosed with opioid use disorder, patients need to do only 2 of the following within 12 months:

• Take more of the drug than intended
• Want or try to cut down without success
• Spend a lot of time in getting, using, or recovering from the drug
• Crave the drug
• Fail to meet commitments due to the drug
• Continue to use the drug, even though it causes social or relationship problems
• Give up or reduce other activities because of the drug
• Use the drug even when it isn’t safe
• Continue to use even when it causes physical or psychological problems
• Develop tolerance (but, as noted, not if taking the drug as directed under a doctor’s supervision)
• Experience withdrawal (again, but not if taking the drug under medical supervision).

WHY DO SOME PATIENTS STRUGGLE TO STOP TAKING OPIOIDS?

Studying opioid use disorder as an outcome in large groups of patients is complicated by imperfect medical documentation. However, using pharmacy claims data, researchers can accurately describe opioid prescription patterns in large groups of patients over time. This means we can count how many patients keep taking prescribed opioids but not how many become addicted.

In a country where nearly 40% of adults are prescribed an opioid annually, the question is not why people start taking opioids, but why some have to struggle to stop.² Several recent studies used pharmacy claims data to identify factors that may predict chronic opioid use in patients prescribed opioids for acute pain. The findings suggest that we can better treat acute pain to prevent chronic opioid use.

We don’t yet know how to protect patients like Mary from opioid use disorder, but the following 3 studies have already changed my practice.

HIGHER TOTAL DOSE MEANS HIGHER RISK

[Shah A, Hayes CJ, Martin BC. Characteristics of initial prescription episodes and likelihood of long-term opioid use—United States, 2006–2015. MMWR Morb Mortal Wkly Rep 2017; 66(10):265–269.]

Shah et al³ reported a study of nearly 1.3 million opioid-naive patients who received opioid prescriptions. Of those prescribed at least 1 day of opioids, 6% were still taking them 1 year later, and 2.9% were still taking them 3 years later.

Opioid exposure in acute pain was measured in total “morphine milligram equivalents” (MME), ie, the cumulative amount of opioids prescribed in the treatment episode, standardized across different types of opioids. We usually think of exposure in terms of how many milligrams a patient takes per day, which correlates with mortality in chronic opioid use.⁴ But this study showed a linear relationship between total MME prescribed for acute pain and ongoing opioid use in opioid-naive patients. By itself, the difference between daily and total MME made the article revelatory.

But the study went further, asking how much is too much: ie, What is the cutoff MME above which the patient is at risk of chronic opioid use? The relationship between acute opioid dose and chronic use is linear and starts early. Shah et al suggested that a total threshold of 700 MME predicts chronic opioid use—140 hydrocodone tablets, or 1 month of regular use.³

Many doctors worry that specific opioids such as oxycodone, hydromorphone, and fentanyl may be more habit-forming. Surprisingly, this study showed that these drugs were associated with rates of chronic use similar to those of other opioids when they controlled for potency.

Bottom line. Total opioid use in acute pain was the best predictor of chronic opioid use, and it showed that chronicity begins earlier than thought.

[Barnett ML, Olenski AR, Jena AB. Opioid-prescribing patterns of emergency physicians and risk of long-term use. N Engl J Med 2017; 376(7):663–673.]

Barnett et al⁵ analyzed opioid prescribing for acute pain in the emergency department, using Medicare pharmacy data from 377,629 previously opioid-naive patients. They categorized the emergency providers into quartiles based on the frequency of opioid prescribing.

The relative risk of ongoing opioid use 1 year after being treated by a “high-intensity” prescriber (ie, one in the top quartile) was 30% greater than in similar patients seen by a low-intensity prescriber (ie, one in the bottom quartile). In addition, those who were treated by high-intensity prescribers were more likely to have a serious fall.

In designing the study, the authors assumed that patients visiting an emergency department had their doctor assigned randomly. They controlled for many patient variables that might have confounded the results, such as age, sex, race, depression, medical comorbidities, and geographic region. Were the higher rates of ongoing opioid use in the high-intensity-prescriber group due to the higher prescribing rates of their emergency providers, or did the providers counsel patients differently? This is not known.

Bottom line. Different doctors manage similar patients differently when it comes to pain, and those who prescribe more opioids for acute pain put their patients at risk of chronic opioid use and falls. I don’t want to be a high-intensity opioid prescriber.

SURGERY AND CHRONIC OPIOID USE

[Brummett CM, Waljee JF, Goesling J, et al. New persistent opioid use after minor and major surgical procedures in US adults. JAMA Surg 2017; 152(6):e170504.]

Brummett et al⁶ examined ongoing opioid use after surgery in 36,177 opioid-naive patients and in a nonsurgical control group. After 3 months, 6% of the patients who underwent surgery remained on opioids, compared with only 0.4% of the nonsurgical controls. Whether the surgery was major or minor did not affect the rate of postoperative opioid use.

Risk factors for ongoing opioid use were preexisting addiction to anything (including tobacco), mood disorders, and preoperative pain disorders. These risk factors have previously been reported in nonsurgical patients.⁷

Brummett et al speculated that patients are counseled about postoperative opioids in a way that leads them to overestimate the safety and efficacy of these drugs for treating other common pain conditions.⁶ 

Bottom line. Patients with mental health comorbidities have a hard time stopping opioids. The remarkable finding in this study was the similarity between major and minor surgery in terms of chronic opioid use. If postoperative opioids treat only the pain caused by the surgery, major surgery should be associated with greater opioid use. The similarity suggests that a mechanism other than postoperative pain confers risk of chronic opioid use.

THINKING ABOUT OPIOIDS

Collectively, these articles describe elements of acute pain treatment that correlate with chronic ongoing opioid use: a higher cumulative dose,³ being seen by a physician who prescribes a lot of opioids,⁵ undergoing surgery,⁶ and psychiatric comorbidity.⁶ They made me wonder if opioid use for acute pain acts as an inoculation, analogous to inoculating a Petri dish with bacteria.  The likelihood of chronic opioid use arises from the inoculum dose, the host response, and the context of inoculation. 

These articles do not show how patients taking opioids chronically for pain become addicted. Stumbo et al⁸ interviewed 283 opioid-dependent patients and identified 5 pathways to opioid use disorder, 3 of which were related to pain control: inadequately controlled chronic pain, exposure to opioids during acute pain episodes, and chronic pain in patients who already had substance use disorders. Brat et al⁹ recently estimated the risk of opioid use disorder after receiving opioids postoperatively to be less than 1%, but it increased dramatically with duration of opioid treatment.

A patient who fills an opioid prescription does not necessarily have chronic pain. Nor do all patients with chronic pain require an opioid prescription. These studies did not establish whether the patients had a pain syndrome. In practice, we call our patients who chronically take opioids our “chronic pain patients.” But 40% of Americans have chronic pain, while only 5% take opioids daily for pain.^11,12

We assume that those taking opioids have the most severe pain. But Brummett et al suggested that continued opioid use is predicted less by pain and more by psychiatric comorbidity.⁶ More than half of the opioid prescriptions in the United States are written for patients with serious mental illness, who represent one-sixth of that population.¹¹ Maybe chronic opioid use for pain has more to do with vulnerability to opioids and less to do with a pain syndrome.

I now think about daily opioid use in much the same way as I think about daily prednisone use. Patients on daily prednisone have a characteristic set of medical risks from the prednisone itself, regardless of its indication. Yet we do not consider these patients addicted to prednisone. Opioid use may be similar.

Like most doctors, I am troubled by the continued rise in the opioid overdose rate.¹³ Yet addiction and death from overdose are not the only risks that patients on chronic opioids face; they also have higher rates of falls, cardiovascular death, pneumonia, death from chronic obstructive pulmonary disease, and motor vehicle crashes.^14–17 Patients on chronic opioids for pain have greater mental health comorbidity and worse function.¹⁸

Most concerning, chronic opioid treatment for pain lacks proof of benefit. In fact, a recent study disproved the benefit of opioids for chronic pain compared with nonopioid options.¹⁹ When I meet with patients who are taking chronic opioids for pain, I often can’t identify why the drugs were started or ought to be continued, and I anticipate a bad outcome. Yet the patient is afraid to stop the drug. For these reasons, chronic opioid use for pain strikes me as worth considering separately from opioid use disorder.

The studies described above have had a powerful effect on my clinical care as a hospitalist.

I now talk to all patients starting opioids about how hard it can be to stop. Some patients are defensive at first, believing this does not apply to them. But I politely continue.

People with depression and anxiety can have a harder time stopping opioids. Addiction is both a risk with ongoing opioid use and a possible outcome of acute opioid use.⁸ But one can struggle to stop opioids without being addicted or depressed. Even the healthiest person may wish to continue opioids past the point of benefit.

I am careful not to invalidate the patient’s experience of pain. It is challenging for patients to find the balance between current discomfort and a possible future adverse effect. In these conversations, I imagine how I would want a loved one counseled on their pain control. This centers me as I choose my words and my tone.

I now monitor the total amount of opioid I prescribe for acute pain in addition to the daily dose. I give my patients as few opioids as reasonable, and advise them to take the minimum dose required for tolerable comfort. I offer nonopioid options as the preferred choice, presenting them as effective and safe. I do this irrespective of the indication for opioids.

I limit opioids in all patients, not just those with comorbidities. I include in my shared decision-making process the risk of chronic opioid use when I prescribe opioids for acute pain, carefully distinguishing it from opioid use disorder. Instead of excess opioids, I give patients my office phone number to call in case they struggle. I rarely get calls. But I find patients would rather have access to a doctor than extra pills. And offering them my contact information lets me limit opioids while letting them know that I am committed to their comfort and health.

As an addiction medicine doctor, I consult on patients not taking their opioids as prescribed. Caring for these patients is intellectually and emotionally draining; they suffer daily, and the opioids they take provide a modicum of relief at a high cost. The publications I have discussed here provide insight into how a troubled relationship with opioids begins. I remind myself that these patients have an iatrogenic condition. Their behaviors that we label “aberrant” may reflect an adverse reaction to medications prescribed to them for acute pain.

Mary, my patient with postoperative pain after cholecystectomy, may over time develop opioid use disorder as Heather did. That progression may have begun with the hydrocodone I prescribed and the counseling I gave her, and it may proceed to chronic opioid use and then opioid use disorder.

I am looking closely at the care I give for acute pain in light of these innovative studies. But even more so, they have increased the compassion with which I care for patients like Heather, those harmed by prescribed opioids.

Mary, age 38, was hospitalized for acute cholecystitis requiring laparoscopic surgery. Her hospital course was uneventful. At the time of discharge, I, her inpatient doctor, prescribed 15 hydrocodone tablets for postoperative pain. I never saw her again. Did she struggle to stop taking the hydrocodone I prescribed?

Heather is a 50-year-old patient in my addiction medicine clinic who developed opioid use disorder while being treated for chronic pain. After much hardship and to her credit, she is now in long-term remission. Did her opioid use disorder start with an opioid prescription for an accepted indication?

The issues Mary and Heather face seem unrelated, but these 2 patients may be at different time points in the progression of the same disease. As a hospitalist, I want to optimize the chances that patients taking opioids for acute pain will be able to stop taking them.

CHRONIC USE VS OPIOID USE DISORDER

There is a distinction between chronic use of opioids and opioid use disorder. The latter is also known as addiction.

Patients who take opioids daily do not necessarily have opioid use disorder, even if they have physiologic dependence on them. Physiologic opioid dependence is commonly confused with opioid use disorder, but it is the expected result of regularly taking these drugs.

Opioid use disorder is a chronic disease of the brain characterized by loss of control over opioid use, resulting in harm. The Diagnostic and Statistical Manual, fifth edition, excludes physiologic dependence on opioids (tolerance and withdrawal) from its criteria for opioid use disorder if the patient is taking opioids solely under medical supervision.¹ To be diagnosed with opioid use disorder, patients need to do only 2 of the following within 12 months:

• Take more of the drug than intended
• Want or try to cut down without success
• Spend a lot of time in getting, using, or recovering from the drug
• Crave the drug
• Fail to meet commitments due to the drug
• Continue to use the drug, even though it causes social or relationship problems
• Give up or reduce other activities because of the drug
• Use the drug even when it isn’t safe
• Continue to use even when it causes physical or psychological problems
• Develop tolerance (but, as noted, not if taking the drug as directed under a doctor’s supervision)
• Experience withdrawal (again, but not if taking the drug under medical supervision).

WHY DO SOME PATIENTS STRUGGLE TO STOP TAKING OPIOIDS?

Studying opioid use disorder as an outcome in large groups of patients is complicated by imperfect medical documentation. However, using pharmacy claims data, researchers can accurately describe opioid prescription patterns in large groups of patients over time. This means we can count how many patients keep taking prescribed opioids but not how many become addicted.

In a country where nearly 40% of adults are prescribed an opioid annually, the question is not why people start taking opioids, but why some have to struggle to stop.² Several recent studies used pharmacy claims data to identify factors that may predict chronic opioid use in patients prescribed opioids for acute pain. The findings suggest that we can better treat acute pain to prevent chronic opioid use.

We don’t yet know how to protect patients like Mary from opioid use disorder, but the following 3 studies have already changed my practice.

HIGHER TOTAL DOSE MEANS HIGHER RISK

[Shah A, Hayes CJ, Martin BC. Characteristics of initial prescription episodes and likelihood of long-term opioid use—United States, 2006–2015. MMWR Morb Mortal Wkly Rep 2017; 66(10):265–269.]

Shah et al³ reported a study of nearly 1.3 million opioid-naive patients who received opioid prescriptions. Of those prescribed at least 1 day of opioids, 6% were still taking them 1 year later, and 2.9% were still taking them 3 years later.

Opioid exposure in acute pain was measured in total “morphine milligram equivalents” (MME), ie, the cumulative amount of opioids prescribed in the treatment episode, standardized across different types of opioids. We usually think of exposure in terms of how many milligrams a patient takes per day, which correlates with mortality in chronic opioid use.⁴ But this study showed a linear relationship between total MME prescribed for acute pain and ongoing opioid use in opioid-naive patients. By itself, the difference between daily and total MME made the article revelatory.

But the study went further, asking how much is too much: ie, What is the cutoff MME above which the patient is at risk of chronic opioid use? The relationship between acute opioid dose and chronic use is linear and starts early. Shah et al suggested that a total threshold of 700 MME predicts chronic opioid use—140 hydrocodone tablets, or 1 month of regular use.³

Many doctors worry that specific opioids such as oxycodone, hydromorphone, and fentanyl may be more habit-forming. Surprisingly, this study showed that these drugs were associated with rates of chronic use similar to those of other opioids when they controlled for potency.

Bottom line. Total opioid use in acute pain was the best predictor of chronic opioid use, and it showed that chronicity begins earlier than thought.

[Barnett ML, Olenski AR, Jena AB. Opioid-prescribing patterns of emergency physicians and risk of long-term use. N Engl J Med 2017; 376(7):663–673.]

Barnett et al⁵ analyzed opioid prescribing for acute pain in the emergency department, using Medicare pharmacy data from 377,629 previously opioid-naive patients. They categorized the emergency providers into quartiles based on the frequency of opioid prescribing.

The relative risk of ongoing opioid use 1 year after being treated by a “high-intensity” prescriber (ie, one in the top quartile) was 30% greater than in similar patients seen by a low-intensity prescriber (ie, one in the bottom quartile). In addition, those who were treated by high-intensity prescribers were more likely to have a serious fall.

In designing the study, the authors assumed that patients visiting an emergency department had their doctor assigned randomly. They controlled for many patient variables that might have confounded the results, such as age, sex, race, depression, medical comorbidities, and geographic region. Were the higher rates of ongoing opioid use in the high-intensity-prescriber group due to the higher prescribing rates of their emergency providers, or did the providers counsel patients differently? This is not known.

Bottom line. Different doctors manage similar patients differently when it comes to pain, and those who prescribe more opioids for acute pain put their patients at risk of chronic opioid use and falls. I don’t want to be a high-intensity opioid prescriber.

SURGERY AND CHRONIC OPIOID USE

[Brummett CM, Waljee JF, Goesling J, et al. New persistent opioid use after minor and major surgical procedures in US adults. JAMA Surg 2017; 152(6):e170504.]

Brummett et al⁶ examined ongoing opioid use after surgery in 36,177 opioid-naive patients and in a nonsurgical control group. After 3 months, 6% of the patients who underwent surgery remained on opioids, compared with only 0.4% of the nonsurgical controls. Whether the surgery was major or minor did not affect the rate of postoperative opioid use.

Risk factors for ongoing opioid use were preexisting addiction to anything (including tobacco), mood disorders, and preoperative pain disorders. These risk factors have previously been reported in nonsurgical patients.⁷

Brummett et al speculated that patients are counseled about postoperative opioids in a way that leads them to overestimate the safety and efficacy of these drugs for treating other common pain conditions.⁶ 

Bottom line. Patients with mental health comorbidities have a hard time stopping opioids. The remarkable finding in this study was the similarity between major and minor surgery in terms of chronic opioid use. If postoperative opioids treat only the pain caused by the surgery, major surgery should be associated with greater opioid use. The similarity suggests that a mechanism other than postoperative pain confers risk of chronic opioid use.

THINKING ABOUT OPIOIDS

Collectively, these articles describe elements of acute pain treatment that correlate with chronic ongoing opioid use: a higher cumulative dose,³ being seen by a physician who prescribes a lot of opioids,⁵ undergoing surgery,⁶ and psychiatric comorbidity.⁶ They made me wonder if opioid use for acute pain acts as an inoculation, analogous to inoculating a Petri dish with bacteria.  The likelihood of chronic opioid use arises from the inoculum dose, the host response, and the context of inoculation. 

These articles do not show how patients taking opioids chronically for pain become addicted. Stumbo et al⁸ interviewed 283 opioid-dependent patients and identified 5 pathways to opioid use disorder, 3 of which were related to pain control: inadequately controlled chronic pain, exposure to opioids during acute pain episodes, and chronic pain in patients who already had substance use disorders. Brat et al⁹ recently estimated the risk of opioid use disorder after receiving opioids postoperatively to be less than 1%, but it increased dramatically with duration of opioid treatment.

A patient who fills an opioid prescription does not necessarily have chronic pain. Nor do all patients with chronic pain require an opioid prescription. These studies did not establish whether the patients had a pain syndrome. In practice, we call our patients who chronically take opioids our “chronic pain patients.” But 40% of Americans have chronic pain, while only 5% take opioids daily for pain.^11,12

We assume that those taking opioids have the most severe pain. But Brummett et al suggested that continued opioid use is predicted less by pain and more by psychiatric comorbidity.⁶ More than half of the opioid prescriptions in the United States are written for patients with serious mental illness, who represent one-sixth of that population.¹¹ Maybe chronic opioid use for pain has more to do with vulnerability to opioids and less to do with a pain syndrome.

I now think about daily opioid use in much the same way as I think about daily prednisone use. Patients on daily prednisone have a characteristic set of medical risks from the prednisone itself, regardless of its indication. Yet we do not consider these patients addicted to prednisone. Opioid use may be similar.

Like most doctors, I am troubled by the continued rise in the opioid overdose rate.¹³ Yet addiction and death from overdose are not the only risks that patients on chronic opioids face; they also have higher rates of falls, cardiovascular death, pneumonia, death from chronic obstructive pulmonary disease, and motor vehicle crashes.^14–17 Patients on chronic opioids for pain have greater mental health comorbidity and worse function.¹⁸

Most concerning, chronic opioid treatment for pain lacks proof of benefit. In fact, a recent study disproved the benefit of opioids for chronic pain compared with nonopioid options.¹⁹ When I meet with patients who are taking chronic opioids for pain, I often can’t identify why the drugs were started or ought to be continued, and I anticipate a bad outcome. Yet the patient is afraid to stop the drug. For these reasons, chronic opioid use for pain strikes me as worth considering separately from opioid use disorder.

The studies described above have had a powerful effect on my clinical care as a hospitalist.

I now talk to all patients starting opioids about how hard it can be to stop. Some patients are defensive at first, believing this does not apply to them. But I politely continue.

People with depression and anxiety can have a harder time stopping opioids. Addiction is both a risk with ongoing opioid use and a possible outcome of acute opioid use.⁸ But one can struggle to stop opioids without being addicted or depressed. Even the healthiest person may wish to continue opioids past the point of benefit.

I am careful not to invalidate the patient’s experience of pain. It is challenging for patients to find the balance between current discomfort and a possible future adverse effect. In these conversations, I imagine how I would want a loved one counseled on their pain control. This centers me as I choose my words and my tone.

I now monitor the total amount of opioid I prescribe for acute pain in addition to the daily dose. I give my patients as few opioids as reasonable, and advise them to take the minimum dose required for tolerable comfort. I offer nonopioid options as the preferred choice, presenting them as effective and safe. I do this irrespective of the indication for opioids.

I limit opioids in all patients, not just those with comorbidities. I include in my shared decision-making process the risk of chronic opioid use when I prescribe opioids for acute pain, carefully distinguishing it from opioid use disorder. Instead of excess opioids, I give patients my office phone number to call in case they struggle. I rarely get calls. But I find patients would rather have access to a doctor than extra pills. And offering them my contact information lets me limit opioids while letting them know that I am committed to their comfort and health.

As an addiction medicine doctor, I consult on patients not taking their opioids as prescribed. Caring for these patients is intellectually and emotionally draining; they suffer daily, and the opioids they take provide a modicum of relief at a high cost. The publications I have discussed here provide insight into how a troubled relationship with opioids begins. I remind myself that these patients have an iatrogenic condition. Their behaviors that we label “aberrant” may reflect an adverse reaction to medications prescribed to them for acute pain.

Mary, my patient with postoperative pain after cholecystectomy, may over time develop opioid use disorder as Heather did. That progression may have begun with the hydrocodone I prescribed and the counseling I gave her, and it may proceed to chronic opioid use and then opioid use disorder.

I am looking closely at the care I give for acute pain in light of these innovative studies. But even more so, they have increased the compassion with which I care for patients like Heather, those harmed by prescribed opioids.

Mary, age 38, was hospitalized for acute cholecystitis requiring laparoscopic surgery. Her hospital course was uneventful. At the time of discharge, I, her inpatient doctor, prescribed 15 hydrocodone tablets for postoperative pain. I never saw her again. Did she struggle to stop taking the hydrocodone I prescribed?

Heather is a 50-year-old patient in my addiction medicine clinic who developed opioid use disorder while being treated for chronic pain. After much hardship and to her credit, she is now in long-term remission. Did her opioid use disorder start with an opioid prescription for an accepted indication?

The issues Mary and Heather face seem unrelated, but these 2 patients may be at different time points in the progression of the same disease. As a hospitalist, I want to optimize the chances that patients taking opioids for acute pain will be able to stop taking them.

CHRONIC USE VS OPIOID USE DISORDER

There is a distinction between chronic use of opioids and opioid use disorder. The latter is also known as addiction.

Patients who take opioids daily do not necessarily have opioid use disorder, even if they have physiologic dependence on them. Physiologic opioid dependence is commonly confused with opioid use disorder, but it is the expected result of regularly taking these drugs.

Opioid use disorder is a chronic disease of the brain characterized by loss of control over opioid use, resulting in harm. The Diagnostic and Statistical Manual, fifth edition, excludes physiologic dependence on opioids (tolerance and withdrawal) from its criteria for opioid use disorder if the patient is taking opioids solely under medical supervision.¹ To be diagnosed with opioid use disorder, patients need to do only 2 of the following within 12 months:

• Take more of the drug than intended
• Want or try to cut down without success
• Spend a lot of time in getting, using, or recovering from the drug
• Crave the drug
• Fail to meet commitments due to the drug
• Continue to use the drug, even though it causes social or relationship problems
• Give up or reduce other activities because of the drug
• Use the drug even when it isn’t safe
• Continue to use even when it causes physical or psychological problems
• Develop tolerance (but, as noted, not if taking the drug as directed under a doctor’s supervision)
• Experience withdrawal (again, but not if taking the drug under medical supervision).

WHY DO SOME PATIENTS STRUGGLE TO STOP TAKING OPIOIDS?

Studying opioid use disorder as an outcome in large groups of patients is complicated by imperfect medical documentation. However, using pharmacy claims data, researchers can accurately describe opioid prescription patterns in large groups of patients over time. This means we can count how many patients keep taking prescribed opioids but not how many become addicted.

In a country where nearly 40% of adults are prescribed an opioid annually, the question is not why people start taking opioids, but why some have to struggle to stop.² Several recent studies used pharmacy claims data to identify factors that may predict chronic opioid use in patients prescribed opioids for acute pain. The findings suggest that we can better treat acute pain to prevent chronic opioid use.

We don’t yet know how to protect patients like Mary from opioid use disorder, but the following 3 studies have already changed my practice.

HIGHER TOTAL DOSE MEANS HIGHER RISK

[Shah A, Hayes CJ, Martin BC. Characteristics of initial prescription episodes and likelihood of long-term opioid use—United States, 2006–2015. MMWR Morb Mortal Wkly Rep 2017; 66(10):265–269.]

Shah et al³ reported a study of nearly 1.3 million opioid-naive patients who received opioid prescriptions. Of those prescribed at least 1 day of opioids, 6% were still taking them 1 year later, and 2.9% were still taking them 3 years later.

Opioid exposure in acute pain was measured in total “morphine milligram equivalents” (MME), ie, the cumulative amount of opioids prescribed in the treatment episode, standardized across different types of opioids. We usually think of exposure in terms of how many milligrams a patient takes per day, which correlates with mortality in chronic opioid use.⁴ But this study showed a linear relationship between total MME prescribed for acute pain and ongoing opioid use in opioid-naive patients. By itself, the difference between daily and total MME made the article revelatory.

But the study went further, asking how much is too much: ie, What is the cutoff MME above which the patient is at risk of chronic opioid use? The relationship between acute opioid dose and chronic use is linear and starts early. Shah et al suggested that a total threshold of 700 MME predicts chronic opioid use—140 hydrocodone tablets, or 1 month of regular use.³

Many doctors worry that specific opioids such as oxycodone, hydromorphone, and fentanyl may be more habit-forming. Surprisingly, this study showed that these drugs were associated with rates of chronic use similar to those of other opioids when they controlled for potency.

Bottom line. Total opioid use in acute pain was the best predictor of chronic opioid use, and it showed that chronicity begins earlier than thought.

[Barnett ML, Olenski AR, Jena AB. Opioid-prescribing patterns of emergency physicians and risk of long-term use. N Engl J Med 2017; 376(7):663–673.]

Barnett et al⁵ analyzed opioid prescribing for acute pain in the emergency department, using Medicare pharmacy data from 377,629 previously opioid-naive patients. They categorized the emergency providers into quartiles based on the frequency of opioid prescribing.

The relative risk of ongoing opioid use 1 year after being treated by a “high-intensity” prescriber (ie, one in the top quartile) was 30% greater than in similar patients seen by a low-intensity prescriber (ie, one in the bottom quartile). In addition, those who were treated by high-intensity prescribers were more likely to have a serious fall.

In designing the study, the authors assumed that patients visiting an emergency department had their doctor assigned randomly. They controlled for many patient variables that might have confounded the results, such as age, sex, race, depression, medical comorbidities, and geographic region. Were the higher rates of ongoing opioid use in the high-intensity-prescriber group due to the higher prescribing rates of their emergency providers, or did the providers counsel patients differently? This is not known.

Bottom line. Different doctors manage similar patients differently when it comes to pain, and those who prescribe more opioids for acute pain put their patients at risk of chronic opioid use and falls. I don’t want to be a high-intensity opioid prescriber.

SURGERY AND CHRONIC OPIOID USE

[Brummett CM, Waljee JF, Goesling J, et al. New persistent opioid use after minor and major surgical procedures in US adults. JAMA Surg 2017; 152(6):e170504.]

Brummett et al⁶ examined ongoing opioid use after surgery in 36,177 opioid-naive patients and in a nonsurgical control group. After 3 months, 6% of the patients who underwent surgery remained on opioids, compared with only 0.4% of the nonsurgical controls. Whether the surgery was major or minor did not affect the rate of postoperative opioid use.

Risk factors for ongoing opioid use were preexisting addiction to anything (including tobacco), mood disorders, and preoperative pain disorders. These risk factors have previously been reported in nonsurgical patients.⁷

Brummett et al speculated that patients are counseled about postoperative opioids in a way that leads them to overestimate the safety and efficacy of these drugs for treating other common pain conditions.⁶ 

Bottom line. Patients with mental health comorbidities have a hard time stopping opioids. The remarkable finding in this study was the similarity between major and minor surgery in terms of chronic opioid use. If postoperative opioids treat only the pain caused by the surgery, major surgery should be associated with greater opioid use. The similarity suggests that a mechanism other than postoperative pain confers risk of chronic opioid use.

THINKING ABOUT OPIOIDS

Collectively, these articles describe elements of acute pain treatment that correlate with chronic ongoing opioid use: a higher cumulative dose,³ being seen by a physician who prescribes a lot of opioids,⁵ undergoing surgery,⁶ and psychiatric comorbidity.⁶ They made me wonder if opioid use for acute pain acts as an inoculation, analogous to inoculating a Petri dish with bacteria.  The likelihood of chronic opioid use arises from the inoculum dose, the host response, and the context of inoculation. 

These articles do not show how patients taking opioids chronically for pain become addicted. Stumbo et al⁸ interviewed 283 opioid-dependent patients and identified 5 pathways to opioid use disorder, 3 of which were related to pain control: inadequately controlled chronic pain, exposure to opioids during acute pain episodes, and chronic pain in patients who already had substance use disorders. Brat et al⁹ recently estimated the risk of opioid use disorder after receiving opioids postoperatively to be less than 1%, but it increased dramatically with duration of opioid treatment.

A patient who fills an opioid prescription does not necessarily have chronic pain. Nor do all patients with chronic pain require an opioid prescription. These studies did not establish whether the patients had a pain syndrome. In practice, we call our patients who chronically take opioids our “chronic pain patients.” But 40% of Americans have chronic pain, while only 5% take opioids daily for pain.^11,12

We assume that those taking opioids have the most severe pain. But Brummett et al suggested that continued opioid use is predicted less by pain and more by psychiatric comorbidity.⁶ More than half of the opioid prescriptions in the United States are written for patients with serious mental illness, who represent one-sixth of that population.¹¹ Maybe chronic opioid use for pain has more to do with vulnerability to opioids and less to do with a pain syndrome.

I now think about daily opioid use in much the same way as I think about daily prednisone use. Patients on daily prednisone have a characteristic set of medical risks from the prednisone itself, regardless of its indication. Yet we do not consider these patients addicted to prednisone. Opioid use may be similar.

Like most doctors, I am troubled by the continued rise in the opioid overdose rate.¹³ Yet addiction and death from overdose are not the only risks that patients on chronic opioids face; they also have higher rates of falls, cardiovascular death, pneumonia, death from chronic obstructive pulmonary disease, and motor vehicle crashes.^14–17 Patients on chronic opioids for pain have greater mental health comorbidity and worse function.¹⁸

Most concerning, chronic opioid treatment for pain lacks proof of benefit. In fact, a recent study disproved the benefit of opioids for chronic pain compared with nonopioid options.¹⁹ When I meet with patients who are taking chronic opioids for pain, I often can’t identify why the drugs were started or ought to be continued, and I anticipate a bad outcome. Yet the patient is afraid to stop the drug. For these reasons, chronic opioid use for pain strikes me as worth considering separately from opioid use disorder.

The studies described above have had a powerful effect on my clinical care as a hospitalist.

I now talk to all patients starting opioids about how hard it can be to stop. Some patients are defensive at first, believing this does not apply to them. But I politely continue.

People with depression and anxiety can have a harder time stopping opioids. Addiction is both a risk with ongoing opioid use and a possible outcome of acute opioid use.⁸ But one can struggle to stop opioids without being addicted or depressed. Even the healthiest person may wish to continue opioids past the point of benefit.

I am careful not to invalidate the patient’s experience of pain. It is challenging for patients to find the balance between current discomfort and a possible future adverse effect. In these conversations, I imagine how I would want a loved one counseled on their pain control. This centers me as I choose my words and my tone.

I now monitor the total amount of opioid I prescribe for acute pain in addition to the daily dose. I give my patients as few opioids as reasonable, and advise them to take the minimum dose required for tolerable comfort. I offer nonopioid options as the preferred choice, presenting them as effective and safe. I do this irrespective of the indication for opioids.

I limit opioids in all patients, not just those with comorbidities. I include in my shared decision-making process the risk of chronic opioid use when I prescribe opioids for acute pain, carefully distinguishing it from opioid use disorder. Instead of excess opioids, I give patients my office phone number to call in case they struggle. I rarely get calls. But I find patients would rather have access to a doctor than extra pills. And offering them my contact information lets me limit opioids while letting them know that I am committed to their comfort and health.

As an addiction medicine doctor, I consult on patients not taking their opioids as prescribed. Caring for these patients is intellectually and emotionally draining; they suffer daily, and the opioids they take provide a modicum of relief at a high cost. The publications I have discussed here provide insight into how a troubled relationship with opioids begins. I remind myself that these patients have an iatrogenic condition. Their behaviors that we label “aberrant” may reflect an adverse reaction to medications prescribed to them for acute pain.

Mary, my patient with postoperative pain after cholecystectomy, may over time develop opioid use disorder as Heather did. That progression may have begun with the hydrocodone I prescribed and the counseling I gave her, and it may proceed to chronic opioid use and then opioid use disorder.

I am looking closely at the care I give for acute pain in light of these innovative studies. But even more so, they have increased the compassion with which I care for patients like Heather, those harmed by prescribed opioids.

My urologic career began in the late 1980s, just before prostate-specific antigen (PSA) testing was introduced. Ever since, a busy prostate cancer practice has given me a frontline view of the benefits and possible harms of PSA screening.

See related article

In the pre-PSA era, about half of men with newly diagnosed prostate cancer presented with incurable disease, either locally advanced or metastatic. The most common treatment was bilateral orchiectomy, which was the only safe form of androgen deprivation available.

Fast-forward a few years to the mid-1990s. Within 5 years after the introduction of PSA testing, the rate of incurable disease at diagnosis fell to just 5%, and treatment for localized disease skyrocketed, including radical prostatectomy, external beam radiation, and brachytherapy. As a result of earlier diagnosis and improved treatments, the death rate from prostate cancer in US men has fallen more than 30% since 1990.

The first-hand experience of seeing this massive stage migration to curable disease has forever convinced me that PSA screening is beneficial. Robust statistical models lend credence to this belief, with estimates that screening is responsible for 45% to 70% of this decline in mortality.¹

Fast-forward again to 2012, when the US Preventive Services Task Force (USPSTF) published a strong recommendation against screening. The recommendation had so much force that as recently as 2014, only 11% of men at highest risk of prostate cancer in the Cleveland Clinic system were screened for it,² mirroring national trends.

What happened? Colored by the experience in the era before PSA, when men presented frequently with painful metastatic disease and had an average life expectancy of 18 to 24 months, it was widely believed that all detected prostate cancer required treatment. What was not appreciated was that while PSA detects lots of prostate cancer, the most common reason for PSA levels to reach a range worrisome enough to trigger biopsy was actually benign prostatic hypertrophy.

The resulting increase in the number of biopsies resulted in the detection of a substantial number of low-grade cancers that were never destined to cause clinical harm but that got treated anyway, based on the fear that all cancers had metastatic potential. The USPSTF based its recommendation against screening on the harms caused by this overdetection and overtreatment of nonlethal disease, focusing on risks of biopsy such as sepsis, and on treatment-related adverse effects such as changes in urinary, bowel, and sexual function.

RANDOMIZED TRIALS SHOW A BENEFIT FROM SCREENING

As a result of this controversy, several large randomized trials designed to test whether PSA screening was beneficial were organized and begun in the 1990s, with one in the United States and another in Europe.^3,4 Mature data from both trials have now established that there is indeed benefit to population-level screening.

The US Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (PLCO), was initially reported to show no difference in prostate cancer-specific mortality rates in those screened vs not screened, but because more than 90% of the men in the no-screening arm were screened anyway, that conclusion is erroneous.³

With 13-year follow-up and far less PSA contamination in the unscreened arm, the European Randomized Study of Screening for Prostate Cancer (ERSPC) in men ages 55 to 69 demonstrated a 27% reduction in the rate of death and a 35% reduction in the need for palliative treatments (androgen deprivation or radiation, or both) for metastatic disease in those screened vs not screened, clearly establishing substantial clinical benefit to PSA screening.⁴

A recent analysis of both trials that controlled for PSA drop-ins (comparing those actually screened with those actually not screened) concluded that the benefit of screening in terms of mortality reduction (estimated at about 30%) are equal in both trials.⁵ A large cohort study from Kaiser Permanente with 16-year follow-up has suggested that PSA screening has both a prostate cancer-specific benefit and an overall mortality benefit.⁶

In parallel with the design and completion of these trials, there was a significant effort to better identify and manage patients initially overdiagnosed with nonlethal cancers by developing active surveillance regimens.

This management strategy recognizes that most low-grade cancers pose no short-term risk to the patient’s health or longevity, that definitive therapy can be deferred, and that with regular monitoring by digital rectal examination, PSA measurement, and repeat biopsy, cancers that progress can still be cured. The result of this strategy is a marked reduction in the harms caused by overtreatment (ie, the aforementioned adverse effects), as well as the avoidance of unnecessary treatment in many patients.

A randomized trial and 2 large prospective cohort studies have confirmed the long-term safety of this approach,^7–9 and the development of commercially available, biopsy-based gene expression profiling tools promises to further improve risk stratification at diagnosis and during follow-up for individual patients.¹⁰

NEW USPSTF RECOMMENDATIONS: AN INDIVIDUAL, INFORMED DECISION

Based on the results of the ERSPC and the widespread adoption and safety of active surveillance, which together show benefit to screening and fewer harms in overdetection and overtreatment, in 2018 the USPSTF recast its recommendations. In upgrading the recommendation from “D” to “C,” the recommendation now states that for men ages 55 to 69, PSA screening should be an individual decision after a discussion with an informed provider, although men over 70 are still advised not to undergo screening at all.¹¹

Some may think that this recommendation has arrived just in time, or that it should be  made even stronger to actually recommend screening, as recent data from 2 national registries—the Surveillance, Epidemiology, and End Results program and the National Cancer Database—show that the fall in screening after the 2012 USPSTF guidelines has resulted in an increase in men presenting with advanced stage disease.^12,13 (All of you Back to the Future fans, please return to the mid to late 1980s to see how that plays out.)

So the pendulum has now swung back in favor of screening, largely supported by solid data showing meaningful clinical benefit, better understanding of PSA and prostate cancer biology, and adoption of active surveillance.

AN IDEAL SCREENING PROGRAM

An ideal screening program would detect only biologically significant cancers, thus eliminating overdetection and overtreatment. There is reason for optimism on this front.

Second-generation PSA tests have better diagnostic accuracy for high-grade disease than earlier tests. Two such tests, the Prostate Health Index (Beckman Coulter) and the 4K-score (Opko Health), are commercially available though not usually covered by commercial insurers.¹⁴ A third test, IsoPSA (Cleveland Diagnostics), is under development. Most hospital laboratories will be able to be run this test with no need for a central laboratory.¹⁵ All 3 tests have been shown to reduce unnecessary biopsies (because of a low probability of finding a biologically significant cancer) by 30% to 45% and will help reduce overdetection.

Moreover, multiparametric magnetic resonance imaging of the prostate has been shown to improve detection of high-grade cancers,¹⁶ and a randomized trial has suggested that its incorporation into a screening strategy is cost-effective and could be better than PSA testing plus transrectal ultrasonography alone (the current standard of care).¹⁷

Several risk scores based on germline genomics also hold promise for better identifying those at risk and for helping to de-intensify screening for those unlikely to have high-grade cancer.¹⁸

Screening for prostate cancer reduces mortality rates and the burden of metastatic disease, and the paradigm continues to evolve. Men at risk by virtue of age (55 to 69, and healthy men > 70), family history, race, and newly identified factors (germline genetics) all deserve an informed discussion on the benefits and risks of screening

My urologic career began in the late 1980s, just before prostate-specific antigen (PSA) testing was introduced. Ever since, a busy prostate cancer practice has given me a frontline view of the benefits and possible harms of PSA screening.

See related article

In the pre-PSA era, about half of men with newly diagnosed prostate cancer presented with incurable disease, either locally advanced or metastatic. The most common treatment was bilateral orchiectomy, which was the only safe form of androgen deprivation available.

Fast-forward a few years to the mid-1990s. Within 5 years after the introduction of PSA testing, the rate of incurable disease at diagnosis fell to just 5%, and treatment for localized disease skyrocketed, including radical prostatectomy, external beam radiation, and brachytherapy. As a result of earlier diagnosis and improved treatments, the death rate from prostate cancer in US men has fallen more than 30% since 1990.

The first-hand experience of seeing this massive stage migration to curable disease has forever convinced me that PSA screening is beneficial. Robust statistical models lend credence to this belief, with estimates that screening is responsible for 45% to 70% of this decline in mortality.¹

Fast-forward again to 2012, when the US Preventive Services Task Force (USPSTF) published a strong recommendation against screening. The recommendation had so much force that as recently as 2014, only 11% of men at highest risk of prostate cancer in the Cleveland Clinic system were screened for it,² mirroring national trends.

What happened? Colored by the experience in the era before PSA, when men presented frequently with painful metastatic disease and had an average life expectancy of 18 to 24 months, it was widely believed that all detected prostate cancer required treatment. What was not appreciated was that while PSA detects lots of prostate cancer, the most common reason for PSA levels to reach a range worrisome enough to trigger biopsy was actually benign prostatic hypertrophy.

The resulting increase in the number of biopsies resulted in the detection of a substantial number of low-grade cancers that were never destined to cause clinical harm but that got treated anyway, based on the fear that all cancers had metastatic potential. The USPSTF based its recommendation against screening on the harms caused by this overdetection and overtreatment of nonlethal disease, focusing on risks of biopsy such as sepsis, and on treatment-related adverse effects such as changes in urinary, bowel, and sexual function.

RANDOMIZED TRIALS SHOW A BENEFIT FROM SCREENING

As a result of this controversy, several large randomized trials designed to test whether PSA screening was beneficial were organized and begun in the 1990s, with one in the United States and another in Europe.^3,4 Mature data from both trials have now established that there is indeed benefit to population-level screening.

The US Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (PLCO), was initially reported to show no difference in prostate cancer-specific mortality rates in those screened vs not screened, but because more than 90% of the men in the no-screening arm were screened anyway, that conclusion is erroneous.³

With 13-year follow-up and far less PSA contamination in the unscreened arm, the European Randomized Study of Screening for Prostate Cancer (ERSPC) in men ages 55 to 69 demonstrated a 27% reduction in the rate of death and a 35% reduction in the need for palliative treatments (androgen deprivation or radiation, or both) for metastatic disease in those screened vs not screened, clearly establishing substantial clinical benefit to PSA screening.⁴

A recent analysis of both trials that controlled for PSA drop-ins (comparing those actually screened with those actually not screened) concluded that the benefit of screening in terms of mortality reduction (estimated at about 30%) are equal in both trials.⁵ A large cohort study from Kaiser Permanente with 16-year follow-up has suggested that PSA screening has both a prostate cancer-specific benefit and an overall mortality benefit.⁶

In parallel with the design and completion of these trials, there was a significant effort to better identify and manage patients initially overdiagnosed with nonlethal cancers by developing active surveillance regimens.

This management strategy recognizes that most low-grade cancers pose no short-term risk to the patient’s health or longevity, that definitive therapy can be deferred, and that with regular monitoring by digital rectal examination, PSA measurement, and repeat biopsy, cancers that progress can still be cured. The result of this strategy is a marked reduction in the harms caused by overtreatment (ie, the aforementioned adverse effects), as well as the avoidance of unnecessary treatment in many patients.

A randomized trial and 2 large prospective cohort studies have confirmed the long-term safety of this approach,^7–9 and the development of commercially available, biopsy-based gene expression profiling tools promises to further improve risk stratification at diagnosis and during follow-up for individual patients.¹⁰

NEW USPSTF RECOMMENDATIONS: AN INDIVIDUAL, INFORMED DECISION

Based on the results of the ERSPC and the widespread adoption and safety of active surveillance, which together show benefit to screening and fewer harms in overdetection and overtreatment, in 2018 the USPSTF recast its recommendations. In upgrading the recommendation from “D” to “C,” the recommendation now states that for men ages 55 to 69, PSA screening should be an individual decision after a discussion with an informed provider, although men over 70 are still advised not to undergo screening at all.¹¹

Some may think that this recommendation has arrived just in time, or that it should be  made even stronger to actually recommend screening, as recent data from 2 national registries—the Surveillance, Epidemiology, and End Results program and the National Cancer Database—show that the fall in screening after the 2012 USPSTF guidelines has resulted in an increase in men presenting with advanced stage disease.^12,13 (All of you Back to the Future fans, please return to the mid to late 1980s to see how that plays out.)

So the pendulum has now swung back in favor of screening, largely supported by solid data showing meaningful clinical benefit, better understanding of PSA and prostate cancer biology, and adoption of active surveillance.

AN IDEAL SCREENING PROGRAM

An ideal screening program would detect only biologically significant cancers, thus eliminating overdetection and overtreatment. There is reason for optimism on this front.

Second-generation PSA tests have better diagnostic accuracy for high-grade disease than earlier tests. Two such tests, the Prostate Health Index (Beckman Coulter) and the 4K-score (Opko Health), are commercially available though not usually covered by commercial insurers.¹⁴ A third test, IsoPSA (Cleveland Diagnostics), is under development. Most hospital laboratories will be able to be run this test with no need for a central laboratory.¹⁵ All 3 tests have been shown to reduce unnecessary biopsies (because of a low probability of finding a biologically significant cancer) by 30% to 45% and will help reduce overdetection.

Moreover, multiparametric magnetic resonance imaging of the prostate has been shown to improve detection of high-grade cancers,¹⁶ and a randomized trial has suggested that its incorporation into a screening strategy is cost-effective and could be better than PSA testing plus transrectal ultrasonography alone (the current standard of care).¹⁷

Several risk scores based on germline genomics also hold promise for better identifying those at risk and for helping to de-intensify screening for those unlikely to have high-grade cancer.¹⁸

Screening for prostate cancer reduces mortality rates and the burden of metastatic disease, and the paradigm continues to evolve. Men at risk by virtue of age (55 to 69, and healthy men > 70), family history, race, and newly identified factors (germline genetics) all deserve an informed discussion on the benefits and risks of screening

My urologic career began in the late 1980s, just before prostate-specific antigen (PSA) testing was introduced. Ever since, a busy prostate cancer practice has given me a frontline view of the benefits and possible harms of PSA screening.

See related article

In the pre-PSA era, about half of men with newly diagnosed prostate cancer presented with incurable disease, either locally advanced or metastatic. The most common treatment was bilateral orchiectomy, which was the only safe form of androgen deprivation available.

Fast-forward a few years to the mid-1990s. Within 5 years after the introduction of PSA testing, the rate of incurable disease at diagnosis fell to just 5%, and treatment for localized disease skyrocketed, including radical prostatectomy, external beam radiation, and brachytherapy. As a result of earlier diagnosis and improved treatments, the death rate from prostate cancer in US men has fallen more than 30% since 1990.

The first-hand experience of seeing this massive stage migration to curable disease has forever convinced me that PSA screening is beneficial. Robust statistical models lend credence to this belief, with estimates that screening is responsible for 45% to 70% of this decline in mortality.¹

Fast-forward again to 2012, when the US Preventive Services Task Force (USPSTF) published a strong recommendation against screening. The recommendation had so much force that as recently as 2014, only 11% of men at highest risk of prostate cancer in the Cleveland Clinic system were screened for it,² mirroring national trends.

What happened? Colored by the experience in the era before PSA, when men presented frequently with painful metastatic disease and had an average life expectancy of 18 to 24 months, it was widely believed that all detected prostate cancer required treatment. What was not appreciated was that while PSA detects lots of prostate cancer, the most common reason for PSA levels to reach a range worrisome enough to trigger biopsy was actually benign prostatic hypertrophy.

The resulting increase in the number of biopsies resulted in the detection of a substantial number of low-grade cancers that were never destined to cause clinical harm but that got treated anyway, based on the fear that all cancers had metastatic potential. The USPSTF based its recommendation against screening on the harms caused by this overdetection and overtreatment of nonlethal disease, focusing on risks of biopsy such as sepsis, and on treatment-related adverse effects such as changes in urinary, bowel, and sexual function.

RANDOMIZED TRIALS SHOW A BENEFIT FROM SCREENING

As a result of this controversy, several large randomized trials designed to test whether PSA screening was beneficial were organized and begun in the 1990s, with one in the United States and another in Europe.^3,4 Mature data from both trials have now established that there is indeed benefit to population-level screening.

The US Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (PLCO), was initially reported to show no difference in prostate cancer-specific mortality rates in those screened vs not screened, but because more than 90% of the men in the no-screening arm were screened anyway, that conclusion is erroneous.³

With 13-year follow-up and far less PSA contamination in the unscreened arm, the European Randomized Study of Screening for Prostate Cancer (ERSPC) in men ages 55 to 69 demonstrated a 27% reduction in the rate of death and a 35% reduction in the need for palliative treatments (androgen deprivation or radiation, or both) for metastatic disease in those screened vs not screened, clearly establishing substantial clinical benefit to PSA screening.⁴

A recent analysis of both trials that controlled for PSA drop-ins (comparing those actually screened with those actually not screened) concluded that the benefit of screening in terms of mortality reduction (estimated at about 30%) are equal in both trials.⁵ A large cohort study from Kaiser Permanente with 16-year follow-up has suggested that PSA screening has both a prostate cancer-specific benefit and an overall mortality benefit.⁶

In parallel with the design and completion of these trials, there was a significant effort to better identify and manage patients initially overdiagnosed with nonlethal cancers by developing active surveillance regimens.

This management strategy recognizes that most low-grade cancers pose no short-term risk to the patient’s health or longevity, that definitive therapy can be deferred, and that with regular monitoring by digital rectal examination, PSA measurement, and repeat biopsy, cancers that progress can still be cured. The result of this strategy is a marked reduction in the harms caused by overtreatment (ie, the aforementioned adverse effects), as well as the avoidance of unnecessary treatment in many patients.

A randomized trial and 2 large prospective cohort studies have confirmed the long-term safety of this approach,^7–9 and the development of commercially available, biopsy-based gene expression profiling tools promises to further improve risk stratification at diagnosis and during follow-up for individual patients.¹⁰

NEW USPSTF RECOMMENDATIONS: AN INDIVIDUAL, INFORMED DECISION

Based on the results of the ERSPC and the widespread adoption and safety of active surveillance, which together show benefit to screening and fewer harms in overdetection and overtreatment, in 2018 the USPSTF recast its recommendations. In upgrading the recommendation from “D” to “C,” the recommendation now states that for men ages 55 to 69, PSA screening should be an individual decision after a discussion with an informed provider, although men over 70 are still advised not to undergo screening at all.¹¹

Some may think that this recommendation has arrived just in time, or that it should be  made even stronger to actually recommend screening, as recent data from 2 national registries—the Surveillance, Epidemiology, and End Results program and the National Cancer Database—show that the fall in screening after the 2012 USPSTF guidelines has resulted in an increase in men presenting with advanced stage disease.^12,13 (All of you Back to the Future fans, please return to the mid to late 1980s to see how that plays out.)

So the pendulum has now swung back in favor of screening, largely supported by solid data showing meaningful clinical benefit, better understanding of PSA and prostate cancer biology, and adoption of active surveillance.

AN IDEAL SCREENING PROGRAM

An ideal screening program would detect only biologically significant cancers, thus eliminating overdetection and overtreatment. There is reason for optimism on this front.

Second-generation PSA tests have better diagnostic accuracy for high-grade disease than earlier tests. Two such tests, the Prostate Health Index (Beckman Coulter) and the 4K-score (Opko Health), are commercially available though not usually covered by commercial insurers.¹⁴ A third test, IsoPSA (Cleveland Diagnostics), is under development. Most hospital laboratories will be able to be run this test with no need for a central laboratory.¹⁵ All 3 tests have been shown to reduce unnecessary biopsies (because of a low probability of finding a biologically significant cancer) by 30% to 45% and will help reduce overdetection.

Moreover, multiparametric magnetic resonance imaging of the prostate has been shown to improve detection of high-grade cancers,¹⁶ and a randomized trial has suggested that its incorporation into a screening strategy is cost-effective and could be better than PSA testing plus transrectal ultrasonography alone (the current standard of care).¹⁷

Several risk scores based on germline genomics also hold promise for better identifying those at risk and for helping to de-intensify screening for those unlikely to have high-grade cancer.¹⁸

Screening for prostate cancer reduces mortality rates and the burden of metastatic disease, and the paradigm continues to evolve. Men at risk by virtue of age (55 to 69, and healthy men > 70), family history, race, and newly identified factors (germline genetics) all deserve an informed discussion on the benefits and risks of screening

Peripheral neuropathy is the most common reason for an outpatient neurology visit in the United States and accounts for over $10 billion in healthcare spending each year.^1,2 When the disorder affects only small, thinly myelinated or unmyelinated nerve fibers, it is referred to as small fiber neuropathy, which commonly presents as numbness and burning pain in the feet.

This article details the manifestations and evaluation of small fiber neuropathy, with an eye toward diagnosing an underlying cause amenable to treatment. 

OLDER PATIENTS MOST AFFECTED

The epidemiology of small fiber neuropathy is not well established. It occurs more commonly in older patients, but data are mixed on prevalence by sex.^3–6 In a Dutch study,³ the overall prevalence was at least 53 cases per 100,000, with the highest rate in men over age 65.

CHARACTERISTIC SENSORY DISTURBANCES

Sensations vary in quality and time

Patients with small fiber neuropathy typically present with a symmetric length-dependent (“stocking-glove”) distribution of sensory changes, starting in the feet and gradually ascending up the legs and then to the hands.

Commonly reported neuropathic symptoms include various combinations of burning, numbness, tingling, itching, sunburn-like, and frostbite-like sensations. Nonneuropathic symptoms may include tightness, a vise-like squeezing of the feet, and the sensation of a sock rolled up at the end of the shoe. Cramps or spasms may also be reported but rarely occur in isolation.⁷

Symptoms are typically worse at the end of the day and while sitting or lying down at night. They can arise spontaneously but may also be triggered by something as minor as the touch of clothing or cool air against the skin. Bedsheet sensitivity of the feet is reported so often that it is used as an outcome measure in clinical trials. Symptoms can also be exacer­bated by extremes in ambient temperature and are especially worse in cold weather.

Random patterns suggest an immune cause

Symptoms may also have a non–length-dependent distribution that is asymmetric, patchy, intermittent, and migratory, and can involve the face, proximal limbs, and trunk. Symptoms may vary throughout the day, eg, starting with electric-shock sensations on one side of the face, followed by perineal numbness and then tingling in the arms lasting for a few minutes to several hours. While such patterns may be seen with diabetes and other common etiologies, they often suggest an underlying immune-mediated disorder such as Sjögren syndrome or sarcoidosis.^8–10 Although large fiber polyneuropathy may also be non–length-dependent, the deficits are usually fixed, with no migratory component.

Autonomic features may be prominent

Autonomic symptoms occur in nearly half of patients and can be as troublesome as neuropathic pain.³ Small nerve fibers mediate somatic and autonomic functions, an evolutionary link that may reflect visceral defense mechanisms responding to pain as a signal of danger.¹¹ This may help explain the multi­systemic nature of symptoms, which can include sweating abnormalities, bowel and bladder disturbances, dry eyes, dry mouth, gastrointestinal dysmotility, skin changes (eg, discoloration, loss of hair, shiny skin), sexual dysfunction, orthostatic hypotension, and palpitations. In some cases, isolated dysautonomia may be seen.

TARGETED EXAMINATION

History: Medications, alcohol, infections

When a patient presents with neuropathic pain in the feet, a detailed history should be obtained, including alcohol use, family history of neuropathy, and use of neurotoxic medications such as metronidazole, colchicine, and chemotherapeutic agents.

Human immunodeficiency virus (HIV) and hepatitis C infection are well known to be associated with small fiber neuropathy, so relevant risk factors (eg, blood transfusions, sexual history, intravenous drug use) should be asked about. Recent illnesses and vaccinations are another important line of questioning, as a small-fiber variant of Guillain-Barré syndrome has been described.¹²

Assess reflexes, strength, sensation

On physical examination, particular attention should be focused on searching for abnormalities indicating large nerve fiber involvement (eg, absent deep tendon reflexes, weakness of the toes). However, absent ankle deep tendon reflexes and reduced vibratory sense may also occur in healthy elderly people.

Similarly, proprioception, motor strength, balance, and vibratory sensation are functions of large myelinated nerve fibers, and thus remain unaffected in patients with only small fiber neuropathy.

Evidence of a systemic disorder should also be sought, as it may indicate an underlying etiology.

Although patients with either large or small fiber neuropathy may have subjective hyperesthesia or numbness of the distal lower extremities, the absence of significant abnormalities on neurologic examination should prompt consideration of small fiber neuropathy.

Electromyography worthwhile

Nerve conduction studies and needle electrode examination evaluate only large nerve fiber conditions. While electromyographic results are normal in patients with isolated small fiber neuropathy, the test can help evaluate subclinical large nerve fiber involvement and alternative diagnoses such as bilateral S1 radiculopathy. Nerve conduction studies may be less useful in patients over age 75, as they may lack sural sensory responses because of aging changes.¹³

Skin biopsy easy to do

Skin biopsy for evaluating intraepidermal nerve fiber density is one of the most widely used tests for small fiber neuropathy. This minimally invasive procedure can now be performed in a primary care office using readily available tools or prepackaged kits and analyzed by several commercial laboratories.

Reduced intraepidermal nerve fiber density on skin biopsy has been described in various other conditions such as fibromyalgia and chronic pain syndromes.^16,17 The clinical significance of these findings remains uncertain.

Quantitative sudomotor axon reflex testing

Quantitative sudomotor axon reflex testing (QSART) is a noninvasive autonomic study that assesses the volume of sweat produced by the limbs in response to acetylcholine. A measure of postganglionic sympathetic sudomotor nerve function, QSART has a sensitivity of up to 80% and can be used to diagnose small fiber neuropathy.¹⁸ In a series of 115 patients with sarcoidosis small fiber neuropathy,⁹ the QSART and skin biopsy findings were concordant in 17 cases and complementary in 29, allowing for confirmation of small fiber neuropathy in patients whose condition would have remained undiagnosed had only one test been performed. QSART can also be considered in cases where skin biopsy may be contraindicated (eg, patient use of anticoagulation).  Of note, the study may be affected by a number of external factors, including caffeine, tobacco, antihistamines, and tricyclic antidepressants; these should be held before testing.

Other diagnostic studies

Other tests may be helpful, as follows:

Tilt-table and cardiovagal testing may be useful for patients with orthostasis and palpitations.

Thermoregulatory sweat testing can be used to evaluate patients with abnormal patterns of sweating, eg, hyperhidrosis of the face and head.

INITIAL TESTING FOR AN UNDERLYING CAUSE

Glucose tolerance test for diabetes

Diabetes is the most common identifiable cause of small fiber neuropathy and accounts for about a third of all cases.⁵ Impaired glucose tolerance is also thought to be a risk factor and has been found in up to 50% of idiopathic cases, but the association is still being debated.²¹

While testing for hemoglobin A_1c is more convenient for the patient, especially because it does not require fasting, a 2-hour oral glucose tolerance test is more sensitive for detecting glucose dysmetabolism.²²

Lipid panel for metabolic syndrome

Small fiber neuropathy is associated with individual components of the metabolic syndrome, which include obesity, hyperglycemia, and dyslipidemia. Of these, dyslipidemia has emerged as the primary factor involved in the development of small fiber neuropathy, via an inflammatory pathway or oxidative stress mechanism.^23,24

Vitamin B₁₂ deficiency testing

Vitamin B₁₂ deficiency, a potentially correctable cause of small fiber neuropathy, may be underdiagnosed, especially as values obtained by blood testing may not reflect tissue uptake. Causes of vitamin B₁₂ deficiency include reduced intake, pernicious anemia, and medications that can affect absorption of vitamin B₁₂ (eg, proton pump inhibitors, histamine 2 receptor antagonists, metformin).

Testing should include:

• Complete blood cell count to evaluate for vitamin B₁₂-related macrocytic anemia and other hematologic abnormalities
• Serum vitamin B₁₂ level
• Methylmalonic acid or homocysteine level in patients with subclinical or mild vitamin B₁₂ deficiency, manifested as low to normal vitamin B₁₂ levels (< 400 pg/mL); methylmalonic acid and homocysteine require vitamin B₁₂ as a cofactor for enzymatic conversion, and either or both may be elevated in early vitamin B₁₂ deficiency.

Celiac antibody panel

Celiac disease, a T-cell mediated enteropathy characterized by gluten intolerance and a herpetiform-like rash, can be associated with small fiber neuropathy.²⁵ In some cases, neuropathy symptoms are preceded by the onset of gastrointestinal symptoms, or they may occur in isolation.²⁵

Sjögren syndrome accounts for nearly 10% of cases of small fiber neuropathy. Associated neuropathic symptoms are often non–length-dependent, can precede sicca symptoms for up to 6 years, and in some cases are the sole manifestation of the disease.¹⁰ Small fiber neuropathy may also be associated with vasculitis, systemic lupus erythematosus, and other connective tissue disorders. 

Testing should include:

• Erythrocyte sedimentation rate, C-reactive protein, and antinuclear antibodies: though these are nonspecific markers of inflammation, they may support an immune-mediated etiology if positive
• Extractable nuclear antigen panel: Sjögren syndrome A and B autoantibodies are the most important components in this setting^5,11
• The Schirmer test or salivary gland biopsy should be considered for seronegative patients with sicca or a suspected immune-mediated etiology, as the sensitivity of antibody testing ranges from only 10% to 55%.¹⁰

Thyroid function testing

Hypothyroidism, and less commonly hyperthyroidism, are associated with small fiber neuropathy.

Metabolic tests for liver and kidney disease

Renal insufficiency and liver impairment are well-known causes of small nerve fiber dysfunction. Testing should include:

• Comprehensive metabolic panel
• Gamma-glutamyltransferase if alcohol abuse is suspected, since heavy alcohol use is one of the most common causes of both large and small fiber neuropathy.

HIV and hepatitis C testing

For patients with relevant risk factors, HIV and hepatitis C testing should be part of the initial workup (and as second-tier testing for others). Patients who test positive for hepatitis C should undergo further testing for cryoglobulinemia, which can present with painful small fiber neuropathy.²⁶

Serum and urine immunoelectrophoresis

Paraproteinemia, with causes ranging from monoclonal gammopathy of uncertain significance to multiple myeloma, has been associated with small fiber neuropathy. An abnormal serum or urine immunoelectrophoresis test warrants further investigation and possibly referral to a hematology-oncology specialist.

SECOND-TIER TESTING

Less common treatable causes of small fiber neuropathy may also be evaluated.

Copper, vitamin B₁ (thiamine), or vitamin B₆ (pyridoxine) deficiency testing. Although vitamin B₆ toxicity may also result in neuropathy due to its toxic effect on the dorsal root ganglia, the mildly elevated vitamin B₆ levels often found in patients being evaluated for neuropathy are unlikely to be the primary cause of symptoms. Many laboratories require fasting samples for accurate vitamin B₆ levels.

Angiotensin-converting enzyme levels for sarcoidosis. Small fiber neuropathy is common in sarcoidosis, occurring in more than 30% of patients with systemic disease.²⁷ However, screening for sarcoidosis by measuring serum levels is often falsely positive and is not cost-effective. In a study of 195 patients with idiopathic small fiber neuropathy,¹¹ 44% had an elevated serum level, but no evidence of sarcoidosis was seen on further testing, which included computed tomography of the chest in 29 patients.¹² Thus, this test is best used for patients with evidence of systemic disease.

Amyloid testing for amyloidosis. Fat pad or bone marrow biopsy should be considered in the appropriate clinical setting.

Paraneoplastic autoantibody panel for occult cancer. Such testing may also be considered if clinically warranted. However, if a patient is found to have low positive titers of paraneoplastic antibodies and suspicion is low for an occult cancer (eg, no weight loss or early satiety), repeat confirmatory testing at another laboratory should be done before embarking on an extensive search for malignancy.

Ganglionic acetylcholine receptor antibody testing for autoimmune autonomic ganglionopathy. This should be ordered for patients with prominent autonomic dysfunction. The antibody test can be ordered separately or as part of an autoantibody panel. The antibody may indicate a primary immune-mediated process or a paraneoplastic disease.²⁸

Genetic mutation testing. Recent discoveries of gene mutations leading to peripheral nerve hyperexcitability of voltage-gated sodium channels have elucidated a hereditary cause of small fiber neuropathy in nearly 30% of cases that were once thought to be idiopathic.^29,30 Genetic testing for mutations in SCN9A and SCN10 (which code for the Nav1.7 and Nav1.8 sodium channels, respectively) is commercially available and may be considered for those with a family history of neuropathic pain in the feet or for young, otherwise healthy patients.

Fabry disease is an X-linked lysosomal disorder characterized by angiokeratomas, cardiac and renal impairment, and small fiber neuropathy. Treatment is now available, but screening is not cost-efficient and should only be pursued in patients with other symptoms of the disease.^31,32

OTHER POSSIBLE CAUSES

Guillain-Barré syndrome

A Guillain-Barré syndrome variant has been reported that is characterized by ascending limb paresthesias and cerebrospinal fluid albuminocytologic dissociation in the setting of preserved deep tendon reflexes and normal findings on EMG.¹² The clinical course is similar to that of typical Guillain-Barré syndrome, in that symptoms follow an upper respiratory or gastrointestinal tract infection, reach their nadir at 4 weeks, and then gradually improve. Some patients respond to intravenous immune globulin.

Vaccine-associated

Postvaccination small fiber neuropathy has also been reported. The nature of the association is unclear.³³

Parkinson disease

Small fiber neuropathy is associated with Parkinson disease. It is attributed to a number of proposed factors, including neurodegeneration that occurs parallel to central nervous system decline, as well as intestinal malabsorption with resultant vitamin deficiency.^34,35

Rapid glycemic lowering

Aggressive treatment of diabetes, defined as at least a 2-point reduction of serum hemoglobin A_1c level over 3 months, may result in acute small fiber neuropathy. It manifests as severe distal extremity pain and dysautonomia.

In a retrospective study,³⁶ 104 (10.9%) of 954 patients presenting to a tertiary diabetic clinic developed treatment-induced diabetic neuropathy with symptoms occurring within 8 weeks of rapid glycemic control. The severity of neuropathy correlated with the degree and rate of glycemic lowering. The condition was reversible in some cases.

For patients with an identified cause of neuropathy, targeted treatment offers the best chance of halting progression and possibly improving symptoms. Below are recommendations for addressing neuropathy associated with the common diagnoses.

Diabetes, impaired glucose tolerance, and metabolic syndrome. In addition to glycemic- and lipid-lowering therapies, lifestyle modifications with a specific focus on exercise and nutrition are integral to treating diabetes and related disorders.

In the Look AHEAD (Action for Health in Diabetes) study,³⁷ which evaluated the effects of intensive lifestyle intervention on neuropathy in 5,145 overweight patients with type 2 diabetes, patients in the intervention group had lower pain scores and better touch sensation in the toes compared with controls at 1 year. Differences correlated with the degree of weight loss and reduction of hemoglobin A_1c and lipid levels.

As running and walking may not be feasible for many patients owing to pain, stationary cycling, aqua therapy, and swimming are other options. A stationary recumbent bike may be useful for older patients with balance issues.

Vitamin B₁₂ deficiency. As reduced absorption rather than low dietary intake is the primary cause of vitamin B₁₂ deficiency for many patients, parenteral rather than oral supplementation may be best. A suggested regimen is subcutaneous or intramuscular methylcobalamin injection of 1,000 µg given daily for 1 week, then once weekly for 1 month, followed by a maintenance dose once a month for at least 6 to 12 months. Alternatively, a daily dose of vitamin B₁₂ 1,000 µg can be taken sublingually.

Sjögren syndrome. According to anecdotal case reports, intravenous immune globulin, corticosteroids, and other immunosuppressants help painful small fiber neuropathy and dysautonomia associated with Sjögren syndrome.¹⁰

Sarcoidosis. Sarcoidosis-associated small fiber neuropathy may also respond to intravenous immune globulin, as well as infliximab and combination therapy.⁹ Culver et al³⁸ found that cibinetide, an experimental erythropoetin agonist, resulted in improved corneal nerve fiber measures in patients with small fiber neuropathy associated with sarcoidosis.

Celiac disease. A gluten-free diet is the treatment for celiac disease and can help some patients.

GENERAL MANAGEMENT

For all patients, regardless of whether the cause of small fiber neuropathy has been identified, managing symptoms remains key, as pain and autonomic dysfunction can markedly impair quality of life. A multidisciplinary approach that incorporates pain medications, physical therapy, and lifestyle modifications is ideal. Integrative holistic treatments such as natural supplements, yoga, and other mind-body therapies may also help.

Pain control

Mexiletine, a voltage-gated sodium channel blocker used as an antiarrhythmic, may help refractory pain or hereditary small fiber neuropathy related to sodium channel dysfunction. However, it is not recommended for diabetic neuropathy.³⁹

Combination regimens that use drugs with different mechanisms of action can be effective. In one study, combined gabapentin and nortriptyline were more effective than either drug alone for neuropathic pain.⁴⁰

Inhaled cannabis reduced pain in patients with HIV and diabetic neuropathy in a number of studies. Side effects included euphoria, somnolence, and cognitive impairment.^41,42 The use of medical marijuana is not yet legal nationwide and may affect employability even in states in which it has been legalized.

Owing to the opioid epidemic and high addiction potential, opioids are no longer a preferred recommendation for chronic treatment of noncancer-related neuropathy. A population-based study of 2,892 patients with neuropathy found that those on chronic opioid therapy (≥ 90 days) had worse functional outcomes and higher rates of addiction and overdose than those on short-term therapy.⁴³ However, the opioid agonist tramadol was found to be effective in reducing neuropathic pain and may be a safer option for patients with chronic small fiber neuropathy.⁴⁴

Integrative, holistic therapies

PROGNOSIS

For many patients, small fiber neuropathy is a slowly progressive disorder that reaches a clinical plateau lasting for years, with progression to large fiber involvement reported in 13% to 36% of cases; over half of patients in one series either improved or remained stable over a period of 2 years.^5,57 Long-term studies are needed to fully understand the natural disease course. In the meantime, treating underlying disease and managing symptoms are imperative to patient care.

Peripheral neuropathy is the most common reason for an outpatient neurology visit in the United States and accounts for over $10 billion in healthcare spending each year.^1,2 When the disorder affects only small, thinly myelinated or unmyelinated nerve fibers, it is referred to as small fiber neuropathy, which commonly presents as numbness and burning pain in the feet.

This article details the manifestations and evaluation of small fiber neuropathy, with an eye toward diagnosing an underlying cause amenable to treatment. 

OLDER PATIENTS MOST AFFECTED

The epidemiology of small fiber neuropathy is not well established. It occurs more commonly in older patients, but data are mixed on prevalence by sex.^3–6 In a Dutch study,³ the overall prevalence was at least 53 cases per 100,000, with the highest rate in men over age 65.

CHARACTERISTIC SENSORY DISTURBANCES

Sensations vary in quality and time

Patients with small fiber neuropathy typically present with a symmetric length-dependent (“stocking-glove”) distribution of sensory changes, starting in the feet and gradually ascending up the legs and then to the hands.

Commonly reported neuropathic symptoms include various combinations of burning, numbness, tingling, itching, sunburn-like, and frostbite-like sensations. Nonneuropathic symptoms may include tightness, a vise-like squeezing of the feet, and the sensation of a sock rolled up at the end of the shoe. Cramps or spasms may also be reported but rarely occur in isolation.⁷

Symptoms are typically worse at the end of the day and while sitting or lying down at night. They can arise spontaneously but may also be triggered by something as minor as the touch of clothing or cool air against the skin. Bedsheet sensitivity of the feet is reported so often that it is used as an outcome measure in clinical trials. Symptoms can also be exacer­bated by extremes in ambient temperature and are especially worse in cold weather.

Random patterns suggest an immune cause

Symptoms may also have a non–length-dependent distribution that is asymmetric, patchy, intermittent, and migratory, and can involve the face, proximal limbs, and trunk. Symptoms may vary throughout the day, eg, starting with electric-shock sensations on one side of the face, followed by perineal numbness and then tingling in the arms lasting for a few minutes to several hours. While such patterns may be seen with diabetes and other common etiologies, they often suggest an underlying immune-mediated disorder such as Sjögren syndrome or sarcoidosis.^8–10 Although large fiber polyneuropathy may also be non–length-dependent, the deficits are usually fixed, with no migratory component.

Autonomic features may be prominent

Autonomic symptoms occur in nearly half of patients and can be as troublesome as neuropathic pain.³ Small nerve fibers mediate somatic and autonomic functions, an evolutionary link that may reflect visceral defense mechanisms responding to pain as a signal of danger.¹¹ This may help explain the multi­systemic nature of symptoms, which can include sweating abnormalities, bowel and bladder disturbances, dry eyes, dry mouth, gastrointestinal dysmotility, skin changes (eg, discoloration, loss of hair, shiny skin), sexual dysfunction, orthostatic hypotension, and palpitations. In some cases, isolated dysautonomia may be seen.

TARGETED EXAMINATION

History: Medications, alcohol, infections

When a patient presents with neuropathic pain in the feet, a detailed history should be obtained, including alcohol use, family history of neuropathy, and use of neurotoxic medications such as metronidazole, colchicine, and chemotherapeutic agents.

Human immunodeficiency virus (HIV) and hepatitis C infection are well known to be associated with small fiber neuropathy, so relevant risk factors (eg, blood transfusions, sexual history, intravenous drug use) should be asked about. Recent illnesses and vaccinations are another important line of questioning, as a small-fiber variant of Guillain-Barré syndrome has been described.¹²

Assess reflexes, strength, sensation

On physical examination, particular attention should be focused on searching for abnormalities indicating large nerve fiber involvement (eg, absent deep tendon reflexes, weakness of the toes). However, absent ankle deep tendon reflexes and reduced vibratory sense may also occur in healthy elderly people.

Similarly, proprioception, motor strength, balance, and vibratory sensation are functions of large myelinated nerve fibers, and thus remain unaffected in patients with only small fiber neuropathy.

Evidence of a systemic disorder should also be sought, as it may indicate an underlying etiology.

Although patients with either large or small fiber neuropathy may have subjective hyperesthesia or numbness of the distal lower extremities, the absence of significant abnormalities on neurologic examination should prompt consideration of small fiber neuropathy.

Electromyography worthwhile

Nerve conduction studies and needle electrode examination evaluate only large nerve fiber conditions. While electromyographic results are normal in patients with isolated small fiber neuropathy, the test can help evaluate subclinical large nerve fiber involvement and alternative diagnoses such as bilateral S1 radiculopathy. Nerve conduction studies may be less useful in patients over age 75, as they may lack sural sensory responses because of aging changes.¹³

Skin biopsy easy to do

Skin biopsy for evaluating intraepidermal nerve fiber density is one of the most widely used tests for small fiber neuropathy. This minimally invasive procedure can now be performed in a primary care office using readily available tools or prepackaged kits and analyzed by several commercial laboratories.

Reduced intraepidermal nerve fiber density on skin biopsy has been described in various other conditions such as fibromyalgia and chronic pain syndromes.^16,17 The clinical significance of these findings remains uncertain.

Quantitative sudomotor axon reflex testing

Quantitative sudomotor axon reflex testing (QSART) is a noninvasive autonomic study that assesses the volume of sweat produced by the limbs in response to acetylcholine. A measure of postganglionic sympathetic sudomotor nerve function, QSART has a sensitivity of up to 80% and can be used to diagnose small fiber neuropathy.¹⁸ In a series of 115 patients with sarcoidosis small fiber neuropathy,⁹ the QSART and skin biopsy findings were concordant in 17 cases and complementary in 29, allowing for confirmation of small fiber neuropathy in patients whose condition would have remained undiagnosed had only one test been performed. QSART can also be considered in cases where skin biopsy may be contraindicated (eg, patient use of anticoagulation).  Of note, the study may be affected by a number of external factors, including caffeine, tobacco, antihistamines, and tricyclic antidepressants; these should be held before testing.

Other diagnostic studies

Other tests may be helpful, as follows:

Tilt-table and cardiovagal testing may be useful for patients with orthostasis and palpitations.

Thermoregulatory sweat testing can be used to evaluate patients with abnormal patterns of sweating, eg, hyperhidrosis of the face and head.

INITIAL TESTING FOR AN UNDERLYING CAUSE

Glucose tolerance test for diabetes

Diabetes is the most common identifiable cause of small fiber neuropathy and accounts for about a third of all cases.⁵ Impaired glucose tolerance is also thought to be a risk factor and has been found in up to 50% of idiopathic cases, but the association is still being debated.²¹

While testing for hemoglobin A_1c is more convenient for the patient, especially because it does not require fasting, a 2-hour oral glucose tolerance test is more sensitive for detecting glucose dysmetabolism.²²

Lipid panel for metabolic syndrome

Small fiber neuropathy is associated with individual components of the metabolic syndrome, which include obesity, hyperglycemia, and dyslipidemia. Of these, dyslipidemia has emerged as the primary factor involved in the development of small fiber neuropathy, via an inflammatory pathway or oxidative stress mechanism.^23,24

Vitamin B₁₂ deficiency testing

Vitamin B₁₂ deficiency, a potentially correctable cause of small fiber neuropathy, may be underdiagnosed, especially as values obtained by blood testing may not reflect tissue uptake. Causes of vitamin B₁₂ deficiency include reduced intake, pernicious anemia, and medications that can affect absorption of vitamin B₁₂ (eg, proton pump inhibitors, histamine 2 receptor antagonists, metformin).

Testing should include:

• Complete blood cell count to evaluate for vitamin B₁₂-related macrocytic anemia and other hematologic abnormalities
• Serum vitamin B₁₂ level
• Methylmalonic acid or homocysteine level in patients with subclinical or mild vitamin B₁₂ deficiency, manifested as low to normal vitamin B₁₂ levels (< 400 pg/mL); methylmalonic acid and homocysteine require vitamin B₁₂ as a cofactor for enzymatic conversion, and either or both may be elevated in early vitamin B₁₂ deficiency.

Celiac antibody panel

Celiac disease, a T-cell mediated enteropathy characterized by gluten intolerance and a herpetiform-like rash, can be associated with small fiber neuropathy.²⁵ In some cases, neuropathy symptoms are preceded by the onset of gastrointestinal symptoms, or they may occur in isolation.²⁵

Sjögren syndrome accounts for nearly 10% of cases of small fiber neuropathy. Associated neuropathic symptoms are often non–length-dependent, can precede sicca symptoms for up to 6 years, and in some cases are the sole manifestation of the disease.¹⁰ Small fiber neuropathy may also be associated with vasculitis, systemic lupus erythematosus, and other connective tissue disorders. 

Testing should include:

• Erythrocyte sedimentation rate, C-reactive protein, and antinuclear antibodies: though these are nonspecific markers of inflammation, they may support an immune-mediated etiology if positive
• Extractable nuclear antigen panel: Sjögren syndrome A and B autoantibodies are the most important components in this setting^5,11
• The Schirmer test or salivary gland biopsy should be considered for seronegative patients with sicca or a suspected immune-mediated etiology, as the sensitivity of antibody testing ranges from only 10% to 55%.¹⁰

Thyroid function testing

Hypothyroidism, and less commonly hyperthyroidism, are associated with small fiber neuropathy.

Metabolic tests for liver and kidney disease

Renal insufficiency and liver impairment are well-known causes of small nerve fiber dysfunction. Testing should include:

• Comprehensive metabolic panel
• Gamma-glutamyltransferase if alcohol abuse is suspected, since heavy alcohol use is one of the most common causes of both large and small fiber neuropathy.

HIV and hepatitis C testing

For patients with relevant risk factors, HIV and hepatitis C testing should be part of the initial workup (and as second-tier testing for others). Patients who test positive for hepatitis C should undergo further testing for cryoglobulinemia, which can present with painful small fiber neuropathy.²⁶

Serum and urine immunoelectrophoresis

Paraproteinemia, with causes ranging from monoclonal gammopathy of uncertain significance to multiple myeloma, has been associated with small fiber neuropathy. An abnormal serum or urine immunoelectrophoresis test warrants further investigation and possibly referral to a hematology-oncology specialist.

SECOND-TIER TESTING

Less common treatable causes of small fiber neuropathy may also be evaluated.

Copper, vitamin B₁ (thiamine), or vitamin B₆ (pyridoxine) deficiency testing. Although vitamin B₆ toxicity may also result in neuropathy due to its toxic effect on the dorsal root ganglia, the mildly elevated vitamin B₆ levels often found in patients being evaluated for neuropathy are unlikely to be the primary cause of symptoms. Many laboratories require fasting samples for accurate vitamin B₆ levels.

Angiotensin-converting enzyme levels for sarcoidosis. Small fiber neuropathy is common in sarcoidosis, occurring in more than 30% of patients with systemic disease.²⁷ However, screening for sarcoidosis by measuring serum levels is often falsely positive and is not cost-effective. In a study of 195 patients with idiopathic small fiber neuropathy,¹¹ 44% had an elevated serum level, but no evidence of sarcoidosis was seen on further testing, which included computed tomography of the chest in 29 patients.¹² Thus, this test is best used for patients with evidence of systemic disease.

Amyloid testing for amyloidosis. Fat pad or bone marrow biopsy should be considered in the appropriate clinical setting.

Paraneoplastic autoantibody panel for occult cancer. Such testing may also be considered if clinically warranted. However, if a patient is found to have low positive titers of paraneoplastic antibodies and suspicion is low for an occult cancer (eg, no weight loss or early satiety), repeat confirmatory testing at another laboratory should be done before embarking on an extensive search for malignancy.

Ganglionic acetylcholine receptor antibody testing for autoimmune autonomic ganglionopathy. This should be ordered for patients with prominent autonomic dysfunction. The antibody test can be ordered separately or as part of an autoantibody panel. The antibody may indicate a primary immune-mediated process or a paraneoplastic disease.²⁸

Genetic mutation testing. Recent discoveries of gene mutations leading to peripheral nerve hyperexcitability of voltage-gated sodium channels have elucidated a hereditary cause of small fiber neuropathy in nearly 30% of cases that were once thought to be idiopathic.^29,30 Genetic testing for mutations in SCN9A and SCN10 (which code for the Nav1.7 and Nav1.8 sodium channels, respectively) is commercially available and may be considered for those with a family history of neuropathic pain in the feet or for young, otherwise healthy patients.

Fabry disease is an X-linked lysosomal disorder characterized by angiokeratomas, cardiac and renal impairment, and small fiber neuropathy. Treatment is now available, but screening is not cost-efficient and should only be pursued in patients with other symptoms of the disease.^31,32

OTHER POSSIBLE CAUSES

Guillain-Barré syndrome

A Guillain-Barré syndrome variant has been reported that is characterized by ascending limb paresthesias and cerebrospinal fluid albuminocytologic dissociation in the setting of preserved deep tendon reflexes and normal findings on EMG.¹² The clinical course is similar to that of typical Guillain-Barré syndrome, in that symptoms follow an upper respiratory or gastrointestinal tract infection, reach their nadir at 4 weeks, and then gradually improve. Some patients respond to intravenous immune globulin.

Vaccine-associated

Postvaccination small fiber neuropathy has also been reported. The nature of the association is unclear.³³

Parkinson disease

Small fiber neuropathy is associated with Parkinson disease. It is attributed to a number of proposed factors, including neurodegeneration that occurs parallel to central nervous system decline, as well as intestinal malabsorption with resultant vitamin deficiency.^34,35

Rapid glycemic lowering

Aggressive treatment of diabetes, defined as at least a 2-point reduction of serum hemoglobin A_1c level over 3 months, may result in acute small fiber neuropathy. It manifests as severe distal extremity pain and dysautonomia.

In a retrospective study,³⁶ 104 (10.9%) of 954 patients presenting to a tertiary diabetic clinic developed treatment-induced diabetic neuropathy with symptoms occurring within 8 weeks of rapid glycemic control. The severity of neuropathy correlated with the degree and rate of glycemic lowering. The condition was reversible in some cases.

For patients with an identified cause of neuropathy, targeted treatment offers the best chance of halting progression and possibly improving symptoms. Below are recommendations for addressing neuropathy associated with the common diagnoses.

Diabetes, impaired glucose tolerance, and metabolic syndrome. In addition to glycemic- and lipid-lowering therapies, lifestyle modifications with a specific focus on exercise and nutrition are integral to treating diabetes and related disorders.

In the Look AHEAD (Action for Health in Diabetes) study,³⁷ which evaluated the effects of intensive lifestyle intervention on neuropathy in 5,145 overweight patients with type 2 diabetes, patients in the intervention group had lower pain scores and better touch sensation in the toes compared with controls at 1 year. Differences correlated with the degree of weight loss and reduction of hemoglobin A_1c and lipid levels.

As running and walking may not be feasible for many patients owing to pain, stationary cycling, aqua therapy, and swimming are other options. A stationary recumbent bike may be useful for older patients with balance issues.

Vitamin B₁₂ deficiency. As reduced absorption rather than low dietary intake is the primary cause of vitamin B₁₂ deficiency for many patients, parenteral rather than oral supplementation may be best. A suggested regimen is subcutaneous or intramuscular methylcobalamin injection of 1,000 µg given daily for 1 week, then once weekly for 1 month, followed by a maintenance dose once a month for at least 6 to 12 months. Alternatively, a daily dose of vitamin B₁₂ 1,000 µg can be taken sublingually.

Sjögren syndrome. According to anecdotal case reports, intravenous immune globulin, corticosteroids, and other immunosuppressants help painful small fiber neuropathy and dysautonomia associated with Sjögren syndrome.¹⁰

Sarcoidosis. Sarcoidosis-associated small fiber neuropathy may also respond to intravenous immune globulin, as well as infliximab and combination therapy.⁹ Culver et al³⁸ found that cibinetide, an experimental erythropoetin agonist, resulted in improved corneal nerve fiber measures in patients with small fiber neuropathy associated with sarcoidosis.

Celiac disease. A gluten-free diet is the treatment for celiac disease and can help some patients.

GENERAL MANAGEMENT

For all patients, regardless of whether the cause of small fiber neuropathy has been identified, managing symptoms remains key, as pain and autonomic dysfunction can markedly impair quality of life. A multidisciplinary approach that incorporates pain medications, physical therapy, and lifestyle modifications is ideal. Integrative holistic treatments such as natural supplements, yoga, and other mind-body therapies may also help.

Pain control

Mexiletine, a voltage-gated sodium channel blocker used as an antiarrhythmic, may help refractory pain or hereditary small fiber neuropathy related to sodium channel dysfunction. However, it is not recommended for diabetic neuropathy.³⁹

Combination regimens that use drugs with different mechanisms of action can be effective. In one study, combined gabapentin and nortriptyline were more effective than either drug alone for neuropathic pain.⁴⁰

Inhaled cannabis reduced pain in patients with HIV and diabetic neuropathy in a number of studies. Side effects included euphoria, somnolence, and cognitive impairment.^41,42 The use of medical marijuana is not yet legal nationwide and may affect employability even in states in which it has been legalized.

Owing to the opioid epidemic and high addiction potential, opioids are no longer a preferred recommendation for chronic treatment of noncancer-related neuropathy. A population-based study of 2,892 patients with neuropathy found that those on chronic opioid therapy (≥ 90 days) had worse functional outcomes and higher rates of addiction and overdose than those on short-term therapy.⁴³ However, the opioid agonist tramadol was found to be effective in reducing neuropathic pain and may be a safer option for patients with chronic small fiber neuropathy.⁴⁴

Integrative, holistic therapies

PROGNOSIS

For many patients, small fiber neuropathy is a slowly progressive disorder that reaches a clinical plateau lasting for years, with progression to large fiber involvement reported in 13% to 36% of cases; over half of patients in one series either improved or remained stable over a period of 2 years.^5,57 Long-term studies are needed to fully understand the natural disease course. In the meantime, treating underlying disease and managing symptoms are imperative to patient care.

Peripheral neuropathy is the most common reason for an outpatient neurology visit in the United States and accounts for over $10 billion in healthcare spending each year.^1,2 When the disorder affects only small, thinly myelinated or unmyelinated nerve fibers, it is referred to as small fiber neuropathy, which commonly presents as numbness and burning pain in the feet.

This article details the manifestations and evaluation of small fiber neuropathy, with an eye toward diagnosing an underlying cause amenable to treatment. 

OLDER PATIENTS MOST AFFECTED

The epidemiology of small fiber neuropathy is not well established. It occurs more commonly in older patients, but data are mixed on prevalence by sex.^3–6 In a Dutch study,³ the overall prevalence was at least 53 cases per 100,000, with the highest rate in men over age 65.

CHARACTERISTIC SENSORY DISTURBANCES

Sensations vary in quality and time

Patients with small fiber neuropathy typically present with a symmetric length-dependent (“stocking-glove”) distribution of sensory changes, starting in the feet and gradually ascending up the legs and then to the hands.

Commonly reported neuropathic symptoms include various combinations of burning, numbness, tingling, itching, sunburn-like, and frostbite-like sensations. Nonneuropathic symptoms may include tightness, a vise-like squeezing of the feet, and the sensation of a sock rolled up at the end of the shoe. Cramps or spasms may also be reported but rarely occur in isolation.⁷

Symptoms are typically worse at the end of the day and while sitting or lying down at night. They can arise spontaneously but may also be triggered by something as minor as the touch of clothing or cool air against the skin. Bedsheet sensitivity of the feet is reported so often that it is used as an outcome measure in clinical trials. Symptoms can also be exacer­bated by extremes in ambient temperature and are especially worse in cold weather.

Random patterns suggest an immune cause

Symptoms may also have a non–length-dependent distribution that is asymmetric, patchy, intermittent, and migratory, and can involve the face, proximal limbs, and trunk. Symptoms may vary throughout the day, eg, starting with electric-shock sensations on one side of the face, followed by perineal numbness and then tingling in the arms lasting for a few minutes to several hours. While such patterns may be seen with diabetes and other common etiologies, they often suggest an underlying immune-mediated disorder such as Sjögren syndrome or sarcoidosis.^8–10 Although large fiber polyneuropathy may also be non–length-dependent, the deficits are usually fixed, with no migratory component.

Autonomic features may be prominent

Autonomic symptoms occur in nearly half of patients and can be as troublesome as neuropathic pain.³ Small nerve fibers mediate somatic and autonomic functions, an evolutionary link that may reflect visceral defense mechanisms responding to pain as a signal of danger.¹¹ This may help explain the multi­systemic nature of symptoms, which can include sweating abnormalities, bowel and bladder disturbances, dry eyes, dry mouth, gastrointestinal dysmotility, skin changes (eg, discoloration, loss of hair, shiny skin), sexual dysfunction, orthostatic hypotension, and palpitations. In some cases, isolated dysautonomia may be seen.

TARGETED EXAMINATION

History: Medications, alcohol, infections

When a patient presents with neuropathic pain in the feet, a detailed history should be obtained, including alcohol use, family history of neuropathy, and use of neurotoxic medications such as metronidazole, colchicine, and chemotherapeutic agents.

Human immunodeficiency virus (HIV) and hepatitis C infection are well known to be associated with small fiber neuropathy, so relevant risk factors (eg, blood transfusions, sexual history, intravenous drug use) should be asked about. Recent illnesses and vaccinations are another important line of questioning, as a small-fiber variant of Guillain-Barré syndrome has been described.¹²

Assess reflexes, strength, sensation

On physical examination, particular attention should be focused on searching for abnormalities indicating large nerve fiber involvement (eg, absent deep tendon reflexes, weakness of the toes). However, absent ankle deep tendon reflexes and reduced vibratory sense may also occur in healthy elderly people.

Similarly, proprioception, motor strength, balance, and vibratory sensation are functions of large myelinated nerve fibers, and thus remain unaffected in patients with only small fiber neuropathy.

Evidence of a systemic disorder should also be sought, as it may indicate an underlying etiology.

Although patients with either large or small fiber neuropathy may have subjective hyperesthesia or numbness of the distal lower extremities, the absence of significant abnormalities on neurologic examination should prompt consideration of small fiber neuropathy.

Electromyography worthwhile

Nerve conduction studies and needle electrode examination evaluate only large nerve fiber conditions. While electromyographic results are normal in patients with isolated small fiber neuropathy, the test can help evaluate subclinical large nerve fiber involvement and alternative diagnoses such as bilateral S1 radiculopathy. Nerve conduction studies may be less useful in patients over age 75, as they may lack sural sensory responses because of aging changes.¹³

Skin biopsy easy to do

Skin biopsy for evaluating intraepidermal nerve fiber density is one of the most widely used tests for small fiber neuropathy. This minimally invasive procedure can now be performed in a primary care office using readily available tools or prepackaged kits and analyzed by several commercial laboratories.

Reduced intraepidermal nerve fiber density on skin biopsy has been described in various other conditions such as fibromyalgia and chronic pain syndromes.^16,17 The clinical significance of these findings remains uncertain.

Quantitative sudomotor axon reflex testing

Quantitative sudomotor axon reflex testing (QSART) is a noninvasive autonomic study that assesses the volume of sweat produced by the limbs in response to acetylcholine. A measure of postganglionic sympathetic sudomotor nerve function, QSART has a sensitivity of up to 80% and can be used to diagnose small fiber neuropathy.¹⁸ In a series of 115 patients with sarcoidosis small fiber neuropathy,⁹ the QSART and skin biopsy findings were concordant in 17 cases and complementary in 29, allowing for confirmation of small fiber neuropathy in patients whose condition would have remained undiagnosed had only one test been performed. QSART can also be considered in cases where skin biopsy may be contraindicated (eg, patient use of anticoagulation).  Of note, the study may be affected by a number of external factors, including caffeine, tobacco, antihistamines, and tricyclic antidepressants; these should be held before testing.

Other diagnostic studies

Other tests may be helpful, as follows:

Tilt-table and cardiovagal testing may be useful for patients with orthostasis and palpitations.

Thermoregulatory sweat testing can be used to evaluate patients with abnormal patterns of sweating, eg, hyperhidrosis of the face and head.

INITIAL TESTING FOR AN UNDERLYING CAUSE

Glucose tolerance test for diabetes

Diabetes is the most common identifiable cause of small fiber neuropathy and accounts for about a third of all cases.⁵ Impaired glucose tolerance is also thought to be a risk factor and has been found in up to 50% of idiopathic cases, but the association is still being debated.²¹

While testing for hemoglobin A_1c is more convenient for the patient, especially because it does not require fasting, a 2-hour oral glucose tolerance test is more sensitive for detecting glucose dysmetabolism.²²

Lipid panel for metabolic syndrome

Small fiber neuropathy is associated with individual components of the metabolic syndrome, which include obesity, hyperglycemia, and dyslipidemia. Of these, dyslipidemia has emerged as the primary factor involved in the development of small fiber neuropathy, via an inflammatory pathway or oxidative stress mechanism.^23,24

Vitamin B₁₂ deficiency testing

Vitamin B₁₂ deficiency, a potentially correctable cause of small fiber neuropathy, may be underdiagnosed, especially as values obtained by blood testing may not reflect tissue uptake. Causes of vitamin B₁₂ deficiency include reduced intake, pernicious anemia, and medications that can affect absorption of vitamin B₁₂ (eg, proton pump inhibitors, histamine 2 receptor antagonists, metformin).

Testing should include:

• Complete blood cell count to evaluate for vitamin B₁₂-related macrocytic anemia and other hematologic abnormalities
• Serum vitamin B₁₂ level
• Methylmalonic acid or homocysteine level in patients with subclinical or mild vitamin B₁₂ deficiency, manifested as low to normal vitamin B₁₂ levels (< 400 pg/mL); methylmalonic acid and homocysteine require vitamin B₁₂ as a cofactor for enzymatic conversion, and either or both may be elevated in early vitamin B₁₂ deficiency.

Celiac antibody panel

Celiac disease, a T-cell mediated enteropathy characterized by gluten intolerance and a herpetiform-like rash, can be associated with small fiber neuropathy.²⁵ In some cases, neuropathy symptoms are preceded by the onset of gastrointestinal symptoms, or they may occur in isolation.²⁵

Sjögren syndrome accounts for nearly 10% of cases of small fiber neuropathy. Associated neuropathic symptoms are often non–length-dependent, can precede sicca symptoms for up to 6 years, and in some cases are the sole manifestation of the disease.¹⁰ Small fiber neuropathy may also be associated with vasculitis, systemic lupus erythematosus, and other connective tissue disorders. 

Testing should include:

• Erythrocyte sedimentation rate, C-reactive protein, and antinuclear antibodies: though these are nonspecific markers of inflammation, they may support an immune-mediated etiology if positive
• Extractable nuclear antigen panel: Sjögren syndrome A and B autoantibodies are the most important components in this setting^5,11
• The Schirmer test or salivary gland biopsy should be considered for seronegative patients with sicca or a suspected immune-mediated etiology, as the sensitivity of antibody testing ranges from only 10% to 55%.¹⁰

Thyroid function testing

Hypothyroidism, and less commonly hyperthyroidism, are associated with small fiber neuropathy.

Metabolic tests for liver and kidney disease

Renal insufficiency and liver impairment are well-known causes of small nerve fiber dysfunction. Testing should include:

• Comprehensive metabolic panel
• Gamma-glutamyltransferase if alcohol abuse is suspected, since heavy alcohol use is one of the most common causes of both large and small fiber neuropathy.

HIV and hepatitis C testing

For patients with relevant risk factors, HIV and hepatitis C testing should be part of the initial workup (and as second-tier testing for others). Patients who test positive for hepatitis C should undergo further testing for cryoglobulinemia, which can present with painful small fiber neuropathy.²⁶

Serum and urine immunoelectrophoresis

Paraproteinemia, with causes ranging from monoclonal gammopathy of uncertain significance to multiple myeloma, has been associated with small fiber neuropathy. An abnormal serum or urine immunoelectrophoresis test warrants further investigation and possibly referral to a hematology-oncology specialist.

SECOND-TIER TESTING

Less common treatable causes of small fiber neuropathy may also be evaluated.

Copper, vitamin B₁ (thiamine), or vitamin B₆ (pyridoxine) deficiency testing. Although vitamin B₆ toxicity may also result in neuropathy due to its toxic effect on the dorsal root ganglia, the mildly elevated vitamin B₆ levels often found in patients being evaluated for neuropathy are unlikely to be the primary cause of symptoms. Many laboratories require fasting samples for accurate vitamin B₆ levels.

Angiotensin-converting enzyme levels for sarcoidosis. Small fiber neuropathy is common in sarcoidosis, occurring in more than 30% of patients with systemic disease.²⁷ However, screening for sarcoidosis by measuring serum levels is often falsely positive and is not cost-effective. In a study of 195 patients with idiopathic small fiber neuropathy,¹¹ 44% had an elevated serum level, but no evidence of sarcoidosis was seen on further testing, which included computed tomography of the chest in 29 patients.¹² Thus, this test is best used for patients with evidence of systemic disease.

Amyloid testing for amyloidosis. Fat pad or bone marrow biopsy should be considered in the appropriate clinical setting.

Paraneoplastic autoantibody panel for occult cancer. Such testing may also be considered if clinically warranted. However, if a patient is found to have low positive titers of paraneoplastic antibodies and suspicion is low for an occult cancer (eg, no weight loss or early satiety), repeat confirmatory testing at another laboratory should be done before embarking on an extensive search for malignancy.

Ganglionic acetylcholine receptor antibody testing for autoimmune autonomic ganglionopathy. This should be ordered for patients with prominent autonomic dysfunction. The antibody test can be ordered separately or as part of an autoantibody panel. The antibody may indicate a primary immune-mediated process or a paraneoplastic disease.²⁸

Genetic mutation testing. Recent discoveries of gene mutations leading to peripheral nerve hyperexcitability of voltage-gated sodium channels have elucidated a hereditary cause of small fiber neuropathy in nearly 30% of cases that were once thought to be idiopathic.^29,30 Genetic testing for mutations in SCN9A and SCN10 (which code for the Nav1.7 and Nav1.8 sodium channels, respectively) is commercially available and may be considered for those with a family history of neuropathic pain in the feet or for young, otherwise healthy patients.

Fabry disease is an X-linked lysosomal disorder characterized by angiokeratomas, cardiac and renal impairment, and small fiber neuropathy. Treatment is now available, but screening is not cost-efficient and should only be pursued in patients with other symptoms of the disease.^31,32

OTHER POSSIBLE CAUSES

Guillain-Barré syndrome

A Guillain-Barré syndrome variant has been reported that is characterized by ascending limb paresthesias and cerebrospinal fluid albuminocytologic dissociation in the setting of preserved deep tendon reflexes and normal findings on EMG.¹² The clinical course is similar to that of typical Guillain-Barré syndrome, in that symptoms follow an upper respiratory or gastrointestinal tract infection, reach their nadir at 4 weeks, and then gradually improve. Some patients respond to intravenous immune globulin.

Vaccine-associated

Postvaccination small fiber neuropathy has also been reported. The nature of the association is unclear.³³

Parkinson disease

Small fiber neuropathy is associated with Parkinson disease. It is attributed to a number of proposed factors, including neurodegeneration that occurs parallel to central nervous system decline, as well as intestinal malabsorption with resultant vitamin deficiency.^34,35

Rapid glycemic lowering

Aggressive treatment of diabetes, defined as at least a 2-point reduction of serum hemoglobin A_1c level over 3 months, may result in acute small fiber neuropathy. It manifests as severe distal extremity pain and dysautonomia.

In a retrospective study,³⁶ 104 (10.9%) of 954 patients presenting to a tertiary diabetic clinic developed treatment-induced diabetic neuropathy with symptoms occurring within 8 weeks of rapid glycemic control. The severity of neuropathy correlated with the degree and rate of glycemic lowering. The condition was reversible in some cases.

For patients with an identified cause of neuropathy, targeted treatment offers the best chance of halting progression and possibly improving symptoms. Below are recommendations for addressing neuropathy associated with the common diagnoses.

Diabetes, impaired glucose tolerance, and metabolic syndrome. In addition to glycemic- and lipid-lowering therapies, lifestyle modifications with a specific focus on exercise and nutrition are integral to treating diabetes and related disorders.

In the Look AHEAD (Action for Health in Diabetes) study,³⁷ which evaluated the effects of intensive lifestyle intervention on neuropathy in 5,145 overweight patients with type 2 diabetes, patients in the intervention group had lower pain scores and better touch sensation in the toes compared with controls at 1 year. Differences correlated with the degree of weight loss and reduction of hemoglobin A_1c and lipid levels.

As running and walking may not be feasible for many patients owing to pain, stationary cycling, aqua therapy, and swimming are other options. A stationary recumbent bike may be useful for older patients with balance issues.

Vitamin B₁₂ deficiency. As reduced absorption rather than low dietary intake is the primary cause of vitamin B₁₂ deficiency for many patients, parenteral rather than oral supplementation may be best. A suggested regimen is subcutaneous or intramuscular methylcobalamin injection of 1,000 µg given daily for 1 week, then once weekly for 1 month, followed by a maintenance dose once a month for at least 6 to 12 months. Alternatively, a daily dose of vitamin B₁₂ 1,000 µg can be taken sublingually.

Sjögren syndrome. According to anecdotal case reports, intravenous immune globulin, corticosteroids, and other immunosuppressants help painful small fiber neuropathy and dysautonomia associated with Sjögren syndrome.¹⁰

Sarcoidosis. Sarcoidosis-associated small fiber neuropathy may also respond to intravenous immune globulin, as well as infliximab and combination therapy.⁹ Culver et al³⁸ found that cibinetide, an experimental erythropoetin agonist, resulted in improved corneal nerve fiber measures in patients with small fiber neuropathy associated with sarcoidosis.

Celiac disease. A gluten-free diet is the treatment for celiac disease and can help some patients.

GENERAL MANAGEMENT

For all patients, regardless of whether the cause of small fiber neuropathy has been identified, managing symptoms remains key, as pain and autonomic dysfunction can markedly impair quality of life. A multidisciplinary approach that incorporates pain medications, physical therapy, and lifestyle modifications is ideal. Integrative holistic treatments such as natural supplements, yoga, and other mind-body therapies may also help.

Pain control

Mexiletine, a voltage-gated sodium channel blocker used as an antiarrhythmic, may help refractory pain or hereditary small fiber neuropathy related to sodium channel dysfunction. However, it is not recommended for diabetic neuropathy.³⁹

Combination regimens that use drugs with different mechanisms of action can be effective. In one study, combined gabapentin and nortriptyline were more effective than either drug alone for neuropathic pain.⁴⁰

Inhaled cannabis reduced pain in patients with HIV and diabetic neuropathy in a number of studies. Side effects included euphoria, somnolence, and cognitive impairment.^41,42 The use of medical marijuana is not yet legal nationwide and may affect employability even in states in which it has been legalized.

Owing to the opioid epidemic and high addiction potential, opioids are no longer a preferred recommendation for chronic treatment of noncancer-related neuropathy. A population-based study of 2,892 patients with neuropathy found that those on chronic opioid therapy (≥ 90 days) had worse functional outcomes and higher rates of addiction and overdose than those on short-term therapy.⁴³ However, the opioid agonist tramadol was found to be effective in reducing neuropathic pain and may be a safer option for patients with chronic small fiber neuropathy.⁴⁴

Integrative, holistic therapies

PROGNOSIS

For many patients, small fiber neuropathy is a slowly progressive disorder that reaches a clinical plateau lasting for years, with progression to large fiber involvement reported in 13% to 36% of cases; over half of patients in one series either improved or remained stable over a period of 2 years.^5,57 Long-term studies are needed to fully understand the natural disease course. In the meantime, treating underlying disease and managing symptoms are imperative to patient care.

Many breast cancer survivors and women at high risk of breast cancer suffer from genitourinary syndrome of menopause (GSM), a term that encompasses any urinary, genital, or sexual dysfunction related to a hypoestrogenic state. Although GSM is usually caused by postmenopausal estrogen loss, it can also be caused by cancer treatments such as chemotherapy, radiation, and systemic endocrine therapy (eg, tamoxifen, aromatase inhibitors). These treatments can substantially decrease systemic estrogen levels, causing GSM symptoms that can profoundly worsen quality of life.

Managing GSM in these women poses a dilemma because systemic estrogen-containing therapies can increase the risk of breast cancer, and nonhormonal vaginal lubricants and moisturizers provide only minimal benefit. Fortunately, there are hormonal options, including locally applied estrogen, intravaginal dehydroepiandrosterone (DHEA), and estrogen receptor agonists/antagonists (ospemifene and bazedoxifene).

Here, we review the clinical management of GSM in breast cancer survivors and women at high risk of breast cancer and the efficacy and safety of available treatments, including their impact on breast cancer risk.

DRYNESS, IRRITATION, ATROPHY

The term GSM describes vulvovaginal and genitourinary symptoms associated with estrogen loss after menopause. Common symptoms are vaginal dryness, dyspareunia, irritation of genital skin, and pruritus.

LOCAL ESTROGEN THERAPY

Systemic estrogen therapy is widely used and effective for GSM, but there are concerns that it could increase the risk of breast cancer. After the Women’s Health Initiative in 2002 showed higher rates of cardiovascular disease and breast cancer with systemic estrogen-progestin use,⁵ the use of this hormone therapy declined by approximately 80%.⁶ Since then, healthcare providers have turned to local (ie, vaginal) estrogen therapies to manage GSM. These therapies have several advantages over systemic hormone therapy:

• Lower risk of adverse effects on the breast and cardiovascular system
• Greater efficacy in treating GSM
• In general, no need for progesterone when low-dose local estrogen is given to a woman with a uterus.⁷

Is locally applied estrogen systemically absorbed?

Despite these advantages, concerns remain as to whether vaginal estrogen therapy has adverse consequences associated with systemic absorption, particularly from atrophic vaginal tissues.

Santen,⁸ in a 2015 review of 33 studies, concluded that systemic absorption from low-dose vaginal estrogen is minimal, which provides some rationale for using it to treat vulvovaginal atrophy in postmenopausal women. This finding also suggests that the US Food and Drug Administration (FDA) “black box” warning of possible toxicities with vaginal estrogen is likely overstated, given that serum estrogen levels remained within normal postmenopausal levels.

Nevertheless, many providers are apprehensive about prescribing vaginal estrogen in women with a history of breast cancer because the threshold for systemic estrogen levels associated with breast cancer recurrence has not been established.

ACOG statement. In 2016, a committee of the American College of Obstetricians and Gynecologists cited data showing that low-dose vaginal estrogens do not result in sustained serum estrogen levels exceeding the normal postmenopausal range, and that the use of vaginal estrogens does not increase the risk of cancer recurrence.⁹ However, they recommend caution with vaginal estrogen use, especially in women with a history of estrogen-dependent breast cancer, reserving it for patients with GSM symptoms nonresponsive to nonhormonal treatment and specifying that it be used in low doses.

Vaginal estrogen formulations

Several types of locally applied estrogens are available, each with different properties and affinity for estrogen receptors. These include conjugated estrogens, 17-beta estradiol, estradiol acetate, and estradiol hemihydrate. Three delivery systems are FDA-approved: creams, rings, and tablets (Table 2).

Vaginal creams. Two vaginal creams are available, one (Estrace) containing 17-beta estradiol and the other (Premarin) containing conjugated estrogens.

The FDA-approved dosage for 17-beta estradiol is 2 to 4 g/day for 1 or 2 weeks, then gradually reduced to half the dose for a similar time. Maintenance dosing is 1 g 1 to 3 times per week. However, the ACOG statement notes that the FDA-approved dosages are higher than those proven to be effective and currently used in clinical practice, eg, 0.5 g twice a week.⁹

The FDA-approved dosage of conjugated estrogen cream for moderate to severe dyspareunia is 0.5 g daily for 21 days, then off for 7 days, or 0.5 g twice a week.

Vaginal tablets. The vaginal tablet Vagifem and its generic equivalent Yuvafem contain 10 µg of estradiol hemihydrate. The FDA-approved dosage is 10 µg daily for 2 weeks, followed by 10 µg twice a week, inserted into the lower third of the vagina. This dosage is significantly lower than that of estrogen creams.

Vaginal insert. A newly approved vaginal insert (Imvexxy) contains estradiol 4 µg (the lowest dose of vaginal estradiol available) or 10 µg, in a coconut oil vehicle. Its indications are for moderate to severe dyspareunia due to menopause and atrophic vaginitis due to menopause. A study cited in its package insert (www.accessdata.fda.gov/drugsatfda_docs/label/2018/208564s000lbl.pdf) showed that, in patients who used this product, systemic absorption of estradiol remained within the postmenopausal range. Its effects on breast cancer have not yet been studied.

Vaginal rings. Two vaginal rings are marketed. One (Estring) contains 17-beta estradiol, and the other (Femring) contains estradiol acetate. Only the 17-beta estradiol ring delivers a low dose to vaginal tissues, releasing 7.5 µg/day for 90 days. The estradiol acetate ring releases 0.05 mg/day or 0.10 mg/day and is a systemic treatment meant to be used with a progestin, not for local therapy.

After menopause, as the ovaries stop making estrogen from androstenedione, some production continues in other tissues, with DHEA as the primary precursor of androgens that are ultimately converted to estrogen. This has led to the theory that the cause of GSM is not estrogen deficiency but androgen deficiency. Evidence reviewed by Labrie et al¹¹ shows that vulvovaginal atrophy is caused by decreased DHEA availability, which in turn causes sex steroid deficiency-related menopausal symptoms.¹¹ Thus, it is reasonable to conclude that menopausal symptoms can be relieved by giving DHEA.

This theory has been borne out in clinical trials, in which DHEA in a vaginal tablet formulation increased the maturation of vaginal cells and lowered vaginal pH, leading to relief of GSM symptoms.¹²

The only DHEA product FDA-approved for treating GSM-related symptoms is prasterone (Intrarosa), indicated for moderate to severe dyspareunia due to vulvovaginal atrophy. The recommended dosing is a single 6.5-mg intravaginal tablet (0.5% prasterone) inserted nightly at bedtime. Its efficacy for treating hypoactive sexual desire disorder in postmenopausal women is being investigated.

Breast cancer implications

Because DHEA is converted to estrogen by aromatization, healthcare providers might hesitate to use it in women who have a history of hormone-sensitive cancer. Data on the safety of intravaginal DHEA use in breast cancer survivors are limited. However, studies have found that prasterone has highly beneficial effects on dyspareunia, vaginal dryness, and objective signs of vulvovaginal atrophy without significant drug-related adverse effects.^12,13 In these studies, serum estrogen levels in women treated with DHEA were within the values observed in normal postmenopausal women. In addition, there are no aromatase enzymes in the endometrium, so even high doses of vaginal DHEA (in contrast to high doses of vaginal estrogen) will not stimulate the endometrium.

Clinically, this evidence indicates that DHEA exerts both estrogenic and androgenic activity in the vagina without increasing serum estrogen levels, making it a good alternative to topical estrogen therapy.

OSPEMIFENE: AN ESTROGEN RECEPTOR AGONIST/ANTAGONIST

Ospemifene (Osphena) is an estrogen receptor agonist/antagonist, a class of drugs previously called selective estrogen receptor modulators (SERMs). It is FDA-approved to treat moderate to severe dyspareunia secondary to vulvar and vaginal atrophy.

Ospemifene has unique estrogenic effects on the vaginal mucosa, having been shown to increase the number of epithelial cells, lower the vaginal pH, and decrease the percentage of parabasal cells seen on Papanicolaou smears after 12 weeks of use.¹⁴

Unlike tamoxifen, another drug of this class, ospemifene does not change the endometrial lining.¹⁴ Similarly, ospemifene acts as an estrogenic agonist in bone and, thus, has the potential for use in preventing and managing osteoporosis or for use in women at risk of fractures.

Breast cancer impact

In preclinical trials, ospemifene was found to have antiestrogenic effects on breast tissue, similar to those seen with tamoxifen.

In a model using human tumor grafts, ospemifene decreased tumor growth in mice implanted with estrogen receptor-positive breast cancer cells.¹⁵

In a mouse model using breast cancer cells that were biologically and histologically similar to those of humans, ospemifene had strong antiestrogenic effects on the breast tissue.¹⁶ The evidence suggests that ospemifene has a favorable effect on vulvar and vaginal atrophy.¹⁷

Ospemifene is FDA-approved to treat moderate to severe dyspareunia secondary to menopause. Recommended dosing is 60 mg/day orally with food.

Its antiestrogenic effects on breast tissue make it a promising option for women with a history of estrogen-receptor positive breast cancer. However, further study is needed to fully understand its effects on human breast tissue. According to the manufacturer’s package insert (www.osphena.com/files/pdf/osphena_prescribing_information.pdf), because the drug has not been adequately studied in women with breast cancer, it should not be used in women with known or suspected breast cancer or a history of breast cancer.

CONJUGATED ESTROGENS PLUS BAZEDOXIFENE

The combination of conjugated estrogens and bazedoxifene (Duavee) is a progesterone-free alternative for treating various menopausal symptoms. Bazedoxifene is another estrogen receptor agonist/antagonist, and it was added to counteract estrogen’s effects on the endometrium, thus replacing progesterone. This protective effect has been validated in clinical trials, which also found a favorable safety profile in breast tissue.^18,19

SMART trials. The efficacy of this combination was studied in a series of large phase 3 multicenter trials called the SMART (Selective Estrogens, Menopause, and Response to Therapy) trials.^20–23 Treated patients had markedly fewer vasomotor symptoms at 1 year, along with an increase in superficial cells and intermediate cells of the vaginal epithelium and a decrease in parabasal cells. They also had a substantial decrease in the incidence of dyspareunia.

Its effects on breast tissue were evaluated in the SMART-5 trial. Therapy had no net impact on breast density, suggesting that it has an estrogen-neutral effect on the breast.²³

These results suggest that combined conjugated estrogens and bazedoxifene could be a noteworthy treatment option for GSM in women with a history of estrogen receptor-positive breast cancer, particularly in those with vasomotor symptoms and bone loss. However, the combination has not been studied specifically in breast cancer survivors.

Dosage. The FDA-approved dosing is 20 mg/0.45 mg per day orally to treat vasomotor symptoms, GSM, and osteoporosis in postmenopausal women with a uterus.

LASER THERAPY AND RADIOFREQUENCY HEAT: AN OFF-LABEL OPTION

Low-dose radiofrequency thermal therapy, delivered by carbon dioxide laser or by radiofrequency heat, has been used with some success to treat urinary stress incontinence and vaginal laxity in postpartum women. It may be an option for GSM, although it is not FDA-approved for this indication, and the FDA has recently issued a warning about it.²⁴

Marketing literature promotes laser therapy as an effective option that stimulates vaginal connective tissue to produce new collagen, which then promotes improved blood flow and tissue regeneration for vaginal lubrication and elasticity.

A study comparing fractional carbon dioxide vaginal laser treatment and local estrogen therapy in postmenopausal women with vulvovaginal atrophy found that laser therapy was an effective treatment for vulvovaginal atrophy (dyspareunia, dryness, and burning), both alone and with local estrogen.²⁵

Despite the promising effects of laser therapy for treating vulvovaginal atrophy in GSM, studies have not determined its short-term or long-term safety profile. Furthermore, laser therapy does not improve impaired sexual function, ie, decreased libido, arousal, and sexual satisfaction. Another important consideration is that the cost of laser therapy in 2017 was estimated to be $2,000 to $3,000 per treatment, not covered by healthcare insurance.

Symptoms of GSM are common in breast cancer survivors, both pre- and postmenopausal, especially those treated with tamoxifen or an aromatase inhibitor. Estimates are that 60% of postmenopausal breast cancer survivors and 40% of premenopausal breast cancer survivors suffer from GSM.²⁶ Unfortunately, many women do not seek medical attention for their symptoms.

A variety of hormonal and nonhormonal options are available for these patients. We recommend an interdisciplinary approach to treatment, with the decision to use hormonal options made in collaboration with the patient’s oncologist and the patient herself, in an informed, shared decision-making process that takes into consideration the risks and possible benefits depending on the symptoms.

The first step in selecting a management plan for GSM symptoms in women with breast cancer is to conduct a thorough assessment to provide data for individualizing the care plan. The decision to use a hormonal option should be made in collaboration with a woman’s oncologist and should include an informed decision-making process during which the potential risks and benefits, including the breast cancer impact, are fully disclosed.

Alternatives to systemic estrogen

Vaginal estrogen is an effective and safe option to treat GSM in women with either estrogen receptor-negative or estrogen receptor-positive breast cancer. It often completely cures the symptoms without any noticeable increase in serum estrogen levels.

Vaginal DHEA therapy is a nonestrogen option shown to effectively treat GSM without increasing systemic levels of estrogen or testosterone. This profile makes vaginal DHEA therapy a particularly attractive treatment for symptoms of GSM in women at risk for breast cancer.

Use of an estrogen receptor agonist/antagonist in breast cancer survivors needs careful consideration. Ospemifene has antiestrogenic effects that make it a good option for women with bone loss and those at high risk for breast cancer, but it should not be used concurrently with tamoxifen or raloxifene. Additionally, ospemifene does not cause uterine hyperplasia, so it can be used in women with a uterus.

Although more study is needed, we do have options to improve the overall quality of life in breast cancer survivors with GSM.

Many breast cancer survivors and women at high risk of breast cancer suffer from genitourinary syndrome of menopause (GSM), a term that encompasses any urinary, genital, or sexual dysfunction related to a hypoestrogenic state. Although GSM is usually caused by postmenopausal estrogen loss, it can also be caused by cancer treatments such as chemotherapy, radiation, and systemic endocrine therapy (eg, tamoxifen, aromatase inhibitors). These treatments can substantially decrease systemic estrogen levels, causing GSM symptoms that can profoundly worsen quality of life.

Managing GSM in these women poses a dilemma because systemic estrogen-containing therapies can increase the risk of breast cancer, and nonhormonal vaginal lubricants and moisturizers provide only minimal benefit. Fortunately, there are hormonal options, including locally applied estrogen, intravaginal dehydroepiandrosterone (DHEA), and estrogen receptor agonists/antagonists (ospemifene and bazedoxifene).

Here, we review the clinical management of GSM in breast cancer survivors and women at high risk of breast cancer and the efficacy and safety of available treatments, including their impact on breast cancer risk.

DRYNESS, IRRITATION, ATROPHY

The term GSM describes vulvovaginal and genitourinary symptoms associated with estrogen loss after menopause. Common symptoms are vaginal dryness, dyspareunia, irritation of genital skin, and pruritus.

LOCAL ESTROGEN THERAPY

Systemic estrogen therapy is widely used and effective for GSM, but there are concerns that it could increase the risk of breast cancer. After the Women’s Health Initiative in 2002 showed higher rates of cardiovascular disease and breast cancer with systemic estrogen-progestin use,⁵ the use of this hormone therapy declined by approximately 80%.⁶ Since then, healthcare providers have turned to local (ie, vaginal) estrogen therapies to manage GSM. These therapies have several advantages over systemic hormone therapy:

• Lower risk of adverse effects on the breast and cardiovascular system
• Greater efficacy in treating GSM
• In general, no need for progesterone when low-dose local estrogen is given to a woman with a uterus.⁷

Is locally applied estrogen systemically absorbed?

Despite these advantages, concerns remain as to whether vaginal estrogen therapy has adverse consequences associated with systemic absorption, particularly from atrophic vaginal tissues.

Santen,⁸ in a 2015 review of 33 studies, concluded that systemic absorption from low-dose vaginal estrogen is minimal, which provides some rationale for using it to treat vulvovaginal atrophy in postmenopausal women. This finding also suggests that the US Food and Drug Administration (FDA) “black box” warning of possible toxicities with vaginal estrogen is likely overstated, given that serum estrogen levels remained within normal postmenopausal levels.

Nevertheless, many providers are apprehensive about prescribing vaginal estrogen in women with a history of breast cancer because the threshold for systemic estrogen levels associated with breast cancer recurrence has not been established.

ACOG statement. In 2016, a committee of the American College of Obstetricians and Gynecologists cited data showing that low-dose vaginal estrogens do not result in sustained serum estrogen levels exceeding the normal postmenopausal range, and that the use of vaginal estrogens does not increase the risk of cancer recurrence.⁹ However, they recommend caution with vaginal estrogen use, especially in women with a history of estrogen-dependent breast cancer, reserving it for patients with GSM symptoms nonresponsive to nonhormonal treatment and specifying that it be used in low doses.

Vaginal estrogen formulations

Several types of locally applied estrogens are available, each with different properties and affinity for estrogen receptors. These include conjugated estrogens, 17-beta estradiol, estradiol acetate, and estradiol hemihydrate. Three delivery systems are FDA-approved: creams, rings, and tablets (Table 2).

Vaginal creams. Two vaginal creams are available, one (Estrace) containing 17-beta estradiol and the other (Premarin) containing conjugated estrogens.

The FDA-approved dosage for 17-beta estradiol is 2 to 4 g/day for 1 or 2 weeks, then gradually reduced to half the dose for a similar time. Maintenance dosing is 1 g 1 to 3 times per week. However, the ACOG statement notes that the FDA-approved dosages are higher than those proven to be effective and currently used in clinical practice, eg, 0.5 g twice a week.⁹

The FDA-approved dosage of conjugated estrogen cream for moderate to severe dyspareunia is 0.5 g daily for 21 days, then off for 7 days, or 0.5 g twice a week.

Vaginal tablets. The vaginal tablet Vagifem and its generic equivalent Yuvafem contain 10 µg of estradiol hemihydrate. The FDA-approved dosage is 10 µg daily for 2 weeks, followed by 10 µg twice a week, inserted into the lower third of the vagina. This dosage is significantly lower than that of estrogen creams.

Vaginal insert. A newly approved vaginal insert (Imvexxy) contains estradiol 4 µg (the lowest dose of vaginal estradiol available) or 10 µg, in a coconut oil vehicle. Its indications are for moderate to severe dyspareunia due to menopause and atrophic vaginitis due to menopause. A study cited in its package insert (www.accessdata.fda.gov/drugsatfda_docs/label/2018/208564s000lbl.pdf) showed that, in patients who used this product, systemic absorption of estradiol remained within the postmenopausal range. Its effects on breast cancer have not yet been studied.

Vaginal rings. Two vaginal rings are marketed. One (Estring) contains 17-beta estradiol, and the other (Femring) contains estradiol acetate. Only the 17-beta estradiol ring delivers a low dose to vaginal tissues, releasing 7.5 µg/day for 90 days. The estradiol acetate ring releases 0.05 mg/day or 0.10 mg/day and is a systemic treatment meant to be used with a progestin, not for local therapy.

After menopause, as the ovaries stop making estrogen from androstenedione, some production continues in other tissues, with DHEA as the primary precursor of androgens that are ultimately converted to estrogen. This has led to the theory that the cause of GSM is not estrogen deficiency but androgen deficiency. Evidence reviewed by Labrie et al¹¹ shows that vulvovaginal atrophy is caused by decreased DHEA availability, which in turn causes sex steroid deficiency-related menopausal symptoms.¹¹ Thus, it is reasonable to conclude that menopausal symptoms can be relieved by giving DHEA.

This theory has been borne out in clinical trials, in which DHEA in a vaginal tablet formulation increased the maturation of vaginal cells and lowered vaginal pH, leading to relief of GSM symptoms.¹²

The only DHEA product FDA-approved for treating GSM-related symptoms is prasterone (Intrarosa), indicated for moderate to severe dyspareunia due to vulvovaginal atrophy. The recommended dosing is a single 6.5-mg intravaginal tablet (0.5% prasterone) inserted nightly at bedtime. Its efficacy for treating hypoactive sexual desire disorder in postmenopausal women is being investigated.

Breast cancer implications

Because DHEA is converted to estrogen by aromatization, healthcare providers might hesitate to use it in women who have a history of hormone-sensitive cancer. Data on the safety of intravaginal DHEA use in breast cancer survivors are limited. However, studies have found that prasterone has highly beneficial effects on dyspareunia, vaginal dryness, and objective signs of vulvovaginal atrophy without significant drug-related adverse effects.^12,13 In these studies, serum estrogen levels in women treated with DHEA were within the values observed in normal postmenopausal women. In addition, there are no aromatase enzymes in the endometrium, so even high doses of vaginal DHEA (in contrast to high doses of vaginal estrogen) will not stimulate the endometrium.

Clinically, this evidence indicates that DHEA exerts both estrogenic and androgenic activity in the vagina without increasing serum estrogen levels, making it a good alternative to topical estrogen therapy.

OSPEMIFENE: AN ESTROGEN RECEPTOR AGONIST/ANTAGONIST

Ospemifene (Osphena) is an estrogen receptor agonist/antagonist, a class of drugs previously called selective estrogen receptor modulators (SERMs). It is FDA-approved to treat moderate to severe dyspareunia secondary to vulvar and vaginal atrophy.

Ospemifene has unique estrogenic effects on the vaginal mucosa, having been shown to increase the number of epithelial cells, lower the vaginal pH, and decrease the percentage of parabasal cells seen on Papanicolaou smears after 12 weeks of use.¹⁴

Unlike tamoxifen, another drug of this class, ospemifene does not change the endometrial lining.¹⁴ Similarly, ospemifene acts as an estrogenic agonist in bone and, thus, has the potential for use in preventing and managing osteoporosis or for use in women at risk of fractures.

Breast cancer impact

In preclinical trials, ospemifene was found to have antiestrogenic effects on breast tissue, similar to those seen with tamoxifen.

In a model using human tumor grafts, ospemifene decreased tumor growth in mice implanted with estrogen receptor-positive breast cancer cells.¹⁵

In a mouse model using breast cancer cells that were biologically and histologically similar to those of humans, ospemifene had strong antiestrogenic effects on the breast tissue.¹⁶ The evidence suggests that ospemifene has a favorable effect on vulvar and vaginal atrophy.¹⁷

Ospemifene is FDA-approved to treat moderate to severe dyspareunia secondary to menopause. Recommended dosing is 60 mg/day orally with food.

Its antiestrogenic effects on breast tissue make it a promising option for women with a history of estrogen-receptor positive breast cancer. However, further study is needed to fully understand its effects on human breast tissue. According to the manufacturer’s package insert (www.osphena.com/files/pdf/osphena_prescribing_information.pdf), because the drug has not been adequately studied in women with breast cancer, it should not be used in women with known or suspected breast cancer or a history of breast cancer.

CONJUGATED ESTROGENS PLUS BAZEDOXIFENE

The combination of conjugated estrogens and bazedoxifene (Duavee) is a progesterone-free alternative for treating various menopausal symptoms. Bazedoxifene is another estrogen receptor agonist/antagonist, and it was added to counteract estrogen’s effects on the endometrium, thus replacing progesterone. This protective effect has been validated in clinical trials, which also found a favorable safety profile in breast tissue.^18,19

SMART trials. The efficacy of this combination was studied in a series of large phase 3 multicenter trials called the SMART (Selective Estrogens, Menopause, and Response to Therapy) trials.^20–23 Treated patients had markedly fewer vasomotor symptoms at 1 year, along with an increase in superficial cells and intermediate cells of the vaginal epithelium and a decrease in parabasal cells. They also had a substantial decrease in the incidence of dyspareunia.

Its effects on breast tissue were evaluated in the SMART-5 trial. Therapy had no net impact on breast density, suggesting that it has an estrogen-neutral effect on the breast.²³

These results suggest that combined conjugated estrogens and bazedoxifene could be a noteworthy treatment option for GSM in women with a history of estrogen receptor-positive breast cancer, particularly in those with vasomotor symptoms and bone loss. However, the combination has not been studied specifically in breast cancer survivors.

Dosage. The FDA-approved dosing is 20 mg/0.45 mg per day orally to treat vasomotor symptoms, GSM, and osteoporosis in postmenopausal women with a uterus.

LASER THERAPY AND RADIOFREQUENCY HEAT: AN OFF-LABEL OPTION

Low-dose radiofrequency thermal therapy, delivered by carbon dioxide laser or by radiofrequency heat, has been used with some success to treat urinary stress incontinence and vaginal laxity in postpartum women. It may be an option for GSM, although it is not FDA-approved for this indication, and the FDA has recently issued a warning about it.²⁴

Marketing literature promotes laser therapy as an effective option that stimulates vaginal connective tissue to produce new collagen, which then promotes improved blood flow and tissue regeneration for vaginal lubrication and elasticity.

A study comparing fractional carbon dioxide vaginal laser treatment and local estrogen therapy in postmenopausal women with vulvovaginal atrophy found that laser therapy was an effective treatment for vulvovaginal atrophy (dyspareunia, dryness, and burning), both alone and with local estrogen.²⁵

Despite the promising effects of laser therapy for treating vulvovaginal atrophy in GSM, studies have not determined its short-term or long-term safety profile. Furthermore, laser therapy does not improve impaired sexual function, ie, decreased libido, arousal, and sexual satisfaction. Another important consideration is that the cost of laser therapy in 2017 was estimated to be $2,000 to $3,000 per treatment, not covered by healthcare insurance.

Symptoms of GSM are common in breast cancer survivors, both pre- and postmenopausal, especially those treated with tamoxifen or an aromatase inhibitor. Estimates are that 60% of postmenopausal breast cancer survivors and 40% of premenopausal breast cancer survivors suffer from GSM.²⁶ Unfortunately, many women do not seek medical attention for their symptoms.

A variety of hormonal and nonhormonal options are available for these patients. We recommend an interdisciplinary approach to treatment, with the decision to use hormonal options made in collaboration with the patient’s oncologist and the patient herself, in an informed, shared decision-making process that takes into consideration the risks and possible benefits depending on the symptoms.

The first step in selecting a management plan for GSM symptoms in women with breast cancer is to conduct a thorough assessment to provide data for individualizing the care plan. The decision to use a hormonal option should be made in collaboration with a woman’s oncologist and should include an informed decision-making process during which the potential risks and benefits, including the breast cancer impact, are fully disclosed.

Alternatives to systemic estrogen

Vaginal estrogen is an effective and safe option to treat GSM in women with either estrogen receptor-negative or estrogen receptor-positive breast cancer. It often completely cures the symptoms without any noticeable increase in serum estrogen levels.

Vaginal DHEA therapy is a nonestrogen option shown to effectively treat GSM without increasing systemic levels of estrogen or testosterone. This profile makes vaginal DHEA therapy a particularly attractive treatment for symptoms of GSM in women at risk for breast cancer.

Use of an estrogen receptor agonist/antagonist in breast cancer survivors needs careful consideration. Ospemifene has antiestrogenic effects that make it a good option for women with bone loss and those at high risk for breast cancer, but it should not be used concurrently with tamoxifen or raloxifene. Additionally, ospemifene does not cause uterine hyperplasia, so it can be used in women with a uterus.

Although more study is needed, we do have options to improve the overall quality of life in breast cancer survivors with GSM.

Many breast cancer survivors and women at high risk of breast cancer suffer from genitourinary syndrome of menopause (GSM), a term that encompasses any urinary, genital, or sexual dysfunction related to a hypoestrogenic state. Although GSM is usually caused by postmenopausal estrogen loss, it can also be caused by cancer treatments such as chemotherapy, radiation, and systemic endocrine therapy (eg, tamoxifen, aromatase inhibitors). These treatments can substantially decrease systemic estrogen levels, causing GSM symptoms that can profoundly worsen quality of life.

Managing GSM in these women poses a dilemma because systemic estrogen-containing therapies can increase the risk of breast cancer, and nonhormonal vaginal lubricants and moisturizers provide only minimal benefit. Fortunately, there are hormonal options, including locally applied estrogen, intravaginal dehydroepiandrosterone (DHEA), and estrogen receptor agonists/antagonists (ospemifene and bazedoxifene).

Here, we review the clinical management of GSM in breast cancer survivors and women at high risk of breast cancer and the efficacy and safety of available treatments, including their impact on breast cancer risk.

DRYNESS, IRRITATION, ATROPHY

The term GSM describes vulvovaginal and genitourinary symptoms associated with estrogen loss after menopause. Common symptoms are vaginal dryness, dyspareunia, irritation of genital skin, and pruritus.

LOCAL ESTROGEN THERAPY

Systemic estrogen therapy is widely used and effective for GSM, but there are concerns that it could increase the risk of breast cancer. After the Women’s Health Initiative in 2002 showed higher rates of cardiovascular disease and breast cancer with systemic estrogen-progestin use,⁵ the use of this hormone therapy declined by approximately 80%.⁶ Since then, healthcare providers have turned to local (ie, vaginal) estrogen therapies to manage GSM. These therapies have several advantages over systemic hormone therapy:

• Lower risk of adverse effects on the breast and cardiovascular system
• Greater efficacy in treating GSM
• In general, no need for progesterone when low-dose local estrogen is given to a woman with a uterus.⁷

Is locally applied estrogen systemically absorbed?

Despite these advantages, concerns remain as to whether vaginal estrogen therapy has adverse consequences associated with systemic absorption, particularly from atrophic vaginal tissues.

Santen,⁸ in a 2015 review of 33 studies, concluded that systemic absorption from low-dose vaginal estrogen is minimal, which provides some rationale for using it to treat vulvovaginal atrophy in postmenopausal women. This finding also suggests that the US Food and Drug Administration (FDA) “black box” warning of possible toxicities with vaginal estrogen is likely overstated, given that serum estrogen levels remained within normal postmenopausal levels.

Nevertheless, many providers are apprehensive about prescribing vaginal estrogen in women with a history of breast cancer because the threshold for systemic estrogen levels associated with breast cancer recurrence has not been established.

ACOG statement. In 2016, a committee of the American College of Obstetricians and Gynecologists cited data showing that low-dose vaginal estrogens do not result in sustained serum estrogen levels exceeding the normal postmenopausal range, and that the use of vaginal estrogens does not increase the risk of cancer recurrence.⁹ However, they recommend caution with vaginal estrogen use, especially in women with a history of estrogen-dependent breast cancer, reserving it for patients with GSM symptoms nonresponsive to nonhormonal treatment and specifying that it be used in low doses.

Vaginal estrogen formulations

Several types of locally applied estrogens are available, each with different properties and affinity for estrogen receptors. These include conjugated estrogens, 17-beta estradiol, estradiol acetate, and estradiol hemihydrate. Three delivery systems are FDA-approved: creams, rings, and tablets (Table 2).

Vaginal creams. Two vaginal creams are available, one (Estrace) containing 17-beta estradiol and the other (Premarin) containing conjugated estrogens.

The FDA-approved dosage for 17-beta estradiol is 2 to 4 g/day for 1 or 2 weeks, then gradually reduced to half the dose for a similar time. Maintenance dosing is 1 g 1 to 3 times per week. However, the ACOG statement notes that the FDA-approved dosages are higher than those proven to be effective and currently used in clinical practice, eg, 0.5 g twice a week.⁹

The FDA-approved dosage of conjugated estrogen cream for moderate to severe dyspareunia is 0.5 g daily for 21 days, then off for 7 days, or 0.5 g twice a week.

Vaginal tablets. The vaginal tablet Vagifem and its generic equivalent Yuvafem contain 10 µg of estradiol hemihydrate. The FDA-approved dosage is 10 µg daily for 2 weeks, followed by 10 µg twice a week, inserted into the lower third of the vagina. This dosage is significantly lower than that of estrogen creams.

Vaginal insert. A newly approved vaginal insert (Imvexxy) contains estradiol 4 µg (the lowest dose of vaginal estradiol available) or 10 µg, in a coconut oil vehicle. Its indications are for moderate to severe dyspareunia due to menopause and atrophic vaginitis due to menopause. A study cited in its package insert (www.accessdata.fda.gov/drugsatfda_docs/label/2018/208564s000lbl.pdf) showed that, in patients who used this product, systemic absorption of estradiol remained within the postmenopausal range. Its effects on breast cancer have not yet been studied.

Vaginal rings. Two vaginal rings are marketed. One (Estring) contains 17-beta estradiol, and the other (Femring) contains estradiol acetate. Only the 17-beta estradiol ring delivers a low dose to vaginal tissues, releasing 7.5 µg/day for 90 days. The estradiol acetate ring releases 0.05 mg/day or 0.10 mg/day and is a systemic treatment meant to be used with a progestin, not for local therapy.

After menopause, as the ovaries stop making estrogen from androstenedione, some production continues in other tissues, with DHEA as the primary precursor of androgens that are ultimately converted to estrogen. This has led to the theory that the cause of GSM is not estrogen deficiency but androgen deficiency. Evidence reviewed by Labrie et al¹¹ shows that vulvovaginal atrophy is caused by decreased DHEA availability, which in turn causes sex steroid deficiency-related menopausal symptoms.¹¹ Thus, it is reasonable to conclude that menopausal symptoms can be relieved by giving DHEA.

This theory has been borne out in clinical trials, in which DHEA in a vaginal tablet formulation increased the maturation of vaginal cells and lowered vaginal pH, leading to relief of GSM symptoms.¹²

The only DHEA product FDA-approved for treating GSM-related symptoms is prasterone (Intrarosa), indicated for moderate to severe dyspareunia due to vulvovaginal atrophy. The recommended dosing is a single 6.5-mg intravaginal tablet (0.5% prasterone) inserted nightly at bedtime. Its efficacy for treating hypoactive sexual desire disorder in postmenopausal women is being investigated.

Breast cancer implications

Because DHEA is converted to estrogen by aromatization, healthcare providers might hesitate to use it in women who have a history of hormone-sensitive cancer. Data on the safety of intravaginal DHEA use in breast cancer survivors are limited. However, studies have found that prasterone has highly beneficial effects on dyspareunia, vaginal dryness, and objective signs of vulvovaginal atrophy without significant drug-related adverse effects.^12,13 In these studies, serum estrogen levels in women treated with DHEA were within the values observed in normal postmenopausal women. In addition, there are no aromatase enzymes in the endometrium, so even high doses of vaginal DHEA (in contrast to high doses of vaginal estrogen) will not stimulate the endometrium.

Clinically, this evidence indicates that DHEA exerts both estrogenic and androgenic activity in the vagina without increasing serum estrogen levels, making it a good alternative to topical estrogen therapy.

OSPEMIFENE: AN ESTROGEN RECEPTOR AGONIST/ANTAGONIST

Ospemifene (Osphena) is an estrogen receptor agonist/antagonist, a class of drugs previously called selective estrogen receptor modulators (SERMs). It is FDA-approved to treat moderate to severe dyspareunia secondary to vulvar and vaginal atrophy.

Ospemifene has unique estrogenic effects on the vaginal mucosa, having been shown to increase the number of epithelial cells, lower the vaginal pH, and decrease the percentage of parabasal cells seen on Papanicolaou smears after 12 weeks of use.¹⁴

Unlike tamoxifen, another drug of this class, ospemifene does not change the endometrial lining.¹⁴ Similarly, ospemifene acts as an estrogenic agonist in bone and, thus, has the potential for use in preventing and managing osteoporosis or for use in women at risk of fractures.

Breast cancer impact

In preclinical trials, ospemifene was found to have antiestrogenic effects on breast tissue, similar to those seen with tamoxifen.

In a model using human tumor grafts, ospemifene decreased tumor growth in mice implanted with estrogen receptor-positive breast cancer cells.¹⁵

In a mouse model using breast cancer cells that were biologically and histologically similar to those of humans, ospemifene had strong antiestrogenic effects on the breast tissue.¹⁶ The evidence suggests that ospemifene has a favorable effect on vulvar and vaginal atrophy.¹⁷

Ospemifene is FDA-approved to treat moderate to severe dyspareunia secondary to menopause. Recommended dosing is 60 mg/day orally with food.

Its antiestrogenic effects on breast tissue make it a promising option for women with a history of estrogen-receptor positive breast cancer. However, further study is needed to fully understand its effects on human breast tissue. According to the manufacturer’s package insert (www.osphena.com/files/pdf/osphena_prescribing_information.pdf), because the drug has not been adequately studied in women with breast cancer, it should not be used in women with known or suspected breast cancer or a history of breast cancer.

CONJUGATED ESTROGENS PLUS BAZEDOXIFENE

The combination of conjugated estrogens and bazedoxifene (Duavee) is a progesterone-free alternative for treating various menopausal symptoms. Bazedoxifene is another estrogen receptor agonist/antagonist, and it was added to counteract estrogen’s effects on the endometrium, thus replacing progesterone. This protective effect has been validated in clinical trials, which also found a favorable safety profile in breast tissue.^18,19

SMART trials. The efficacy of this combination was studied in a series of large phase 3 multicenter trials called the SMART (Selective Estrogens, Menopause, and Response to Therapy) trials.^20–23 Treated patients had markedly fewer vasomotor symptoms at 1 year, along with an increase in superficial cells and intermediate cells of the vaginal epithelium and a decrease in parabasal cells. They also had a substantial decrease in the incidence of dyspareunia.

Its effects on breast tissue were evaluated in the SMART-5 trial. Therapy had no net impact on breast density, suggesting that it has an estrogen-neutral effect on the breast.²³

These results suggest that combined conjugated estrogens and bazedoxifene could be a noteworthy treatment option for GSM in women with a history of estrogen receptor-positive breast cancer, particularly in those with vasomotor symptoms and bone loss. However, the combination has not been studied specifically in breast cancer survivors.

Dosage. The FDA-approved dosing is 20 mg/0.45 mg per day orally to treat vasomotor symptoms, GSM, and osteoporosis in postmenopausal women with a uterus.

LASER THERAPY AND RADIOFREQUENCY HEAT: AN OFF-LABEL OPTION

Low-dose radiofrequency thermal therapy, delivered by carbon dioxide laser or by radiofrequency heat, has been used with some success to treat urinary stress incontinence and vaginal laxity in postpartum women. It may be an option for GSM, although it is not FDA-approved for this indication, and the FDA has recently issued a warning about it.²⁴

Marketing literature promotes laser therapy as an effective option that stimulates vaginal connective tissue to produce new collagen, which then promotes improved blood flow and tissue regeneration for vaginal lubrication and elasticity.

A study comparing fractional carbon dioxide vaginal laser treatment and local estrogen therapy in postmenopausal women with vulvovaginal atrophy found that laser therapy was an effective treatment for vulvovaginal atrophy (dyspareunia, dryness, and burning), both alone and with local estrogen.²⁵

Despite the promising effects of laser therapy for treating vulvovaginal atrophy in GSM, studies have not determined its short-term or long-term safety profile. Furthermore, laser therapy does not improve impaired sexual function, ie, decreased libido, arousal, and sexual satisfaction. Another important consideration is that the cost of laser therapy in 2017 was estimated to be $2,000 to $3,000 per treatment, not covered by healthcare insurance.

Symptoms of GSM are common in breast cancer survivors, both pre- and postmenopausal, especially those treated with tamoxifen or an aromatase inhibitor. Estimates are that 60% of postmenopausal breast cancer survivors and 40% of premenopausal breast cancer survivors suffer from GSM.²⁶ Unfortunately, many women do not seek medical attention for their symptoms.

A variety of hormonal and nonhormonal options are available for these patients. We recommend an interdisciplinary approach to treatment, with the decision to use hormonal options made in collaboration with the patient’s oncologist and the patient herself, in an informed, shared decision-making process that takes into consideration the risks and possible benefits depending on the symptoms.

The first step in selecting a management plan for GSM symptoms in women with breast cancer is to conduct a thorough assessment to provide data for individualizing the care plan. The decision to use a hormonal option should be made in collaboration with a woman’s oncologist and should include an informed decision-making process during which the potential risks and benefits, including the breast cancer impact, are fully disclosed.

Alternatives to systemic estrogen

Vaginal estrogen is an effective and safe option to treat GSM in women with either estrogen receptor-negative or estrogen receptor-positive breast cancer. It often completely cures the symptoms without any noticeable increase in serum estrogen levels.

Vaginal DHEA therapy is a nonestrogen option shown to effectively treat GSM without increasing systemic levels of estrogen or testosterone. This profile makes vaginal DHEA therapy a particularly attractive treatment for symptoms of GSM in women at risk for breast cancer.

Use of an estrogen receptor agonist/antagonist in breast cancer survivors needs careful consideration. Ospemifene has antiestrogenic effects that make it a good option for women with bone loss and those at high risk for breast cancer, but it should not be used concurrently with tamoxifen or raloxifene. Additionally, ospemifene does not cause uterine hyperplasia, so it can be used in women with a uterus.

Although more study is needed, we do have options to improve the overall quality of life in breast cancer survivors with GSM.