CtDNA agrees (mostly) with tissue analysis in mCRC

For identifying patients with metastatic colorectal cancer who might benefit from therapy with drugs targeted against the epidermal growth factor receptor (EGFR), analysis of plasma for circulating tumor DNA – aka “liquid biopsy” – is about as capable as and considerably faster than tissue analysis of RAS mutational status, investigators contend.

Among 412 chemotherapy-naive patients with metastatic colorectal cancer (mCRC) for whom both plasma and tissue samples were available, the kappa coefficient (a measure of acceptable concordance) between ctDNA RAS mutation detection and tissue-based analysis was 0.71, just over the minimum 0.7, and the accuracy of the liquid biopsy sampling was 85.2%, reported Pierre Laurent-Puig, MD, PhD, of Sorbonne University in Paris, and his colleagues.

“[E]ven if our results are limited to the techniques used with their analytic sensitivity, we show here for the first time in a prospective study an excellent concordance between plasma and tumor RAS mutation status in metastatic colorectal cancer patients, especially those with liver metastases. These results validate the routine use of plasma RAS analysis in patients with colorectal cancer and liver metastases,” they wrote. The report was published in Annals of Oncology.

The investigators found that ctDNA was more likely to yield inconclusive results in patients without liver metastases. In patients with liver metastases, the accuracy of the liquid biopsy using next-generation sequencing (NGS) alone to detect RAS mutations was 93.5%, and when detection of methylated biomarkers was added in, the accuracy was 97%.

In the AGEO RASANC prospective multicenter study, the investigators prospectively collected plasma samples from patients with mCRC and sent them to a central lab for analysis by NGS with the colon/lung cancer V2 Ampliseq panel and with digital polymerase chain reaction dPCR for genes associated with DNA methylation (WIF1 and NPY).

Matched tissue samples from the same patients were analyzed locally according to routine practice.

As noted before, the kappa coefficient was 0.71, indicating that agreement between the tests was at least 70% better than by chance alone.

In 329 patients who had detectable ctDNA, defined as at least one mutation or one methylated biomarker, the kappa coefficient rose to 89% and the accuracy to 94.8%.

Also as noted, in the 293 patients with liver metastases, the accuracy improved to close to 100% with both NGS and methylated biomarker detection.

“Based solely on the plasma analysis using our prespecified analysis, 14 patients would have received ineffective and potentially deleterious anti-EGFR therapy. All were considered as truly RAS wild-type in their plasma because of the presence of other mutations detected by NGS and/or a positive methylation assay,” the researchers wrote.

The lack of sensitivity of ctDNA in these patients may have been due to the fact that the fraction of mutated alleles in these patients was lower than in patients for whom both plasma and tissue analysis were negative for RAS mutations. All of these patients had early metastases, which could explain why the sensitivity of the plasma assay was lower than in patients with advanced-stage disease, they said.

“On the contrary detection of RAS mutations in plasma but not in tumor cells could exclude some patients from potentially effective anti-EGFR therapy,” they added. They identified eight patients with plasma-positive, tissue-negative discordance, which could be due to errors in tissue sampling due to heterogeneity of mutations within tissues, or to a lack of sensitivity of RAS mutation detection in tissues.

The trial was sponsored by AGEO and supported by a grant from Merck Serono. Dr. Laurent-Puig disclosed grants from AGEO and personal fees from Merck Serono and other companies. Multiple coauthors reported fees from Merck Serono and others.

SOURCE: Laurent-Puig P et al. Ann Oncol. 2018 Feb 9. doi: 10.1093/annonc/mdy061/4846852.

For identifying patients with metastatic colorectal cancer who might benefit from therapy with drugs targeted against the epidermal growth factor receptor (EGFR), analysis of plasma for circulating tumor DNA – aka “liquid biopsy” – is about as capable as and considerably faster than tissue analysis of RAS mutational status, investigators contend.

Among 412 chemotherapy-naive patients with metastatic colorectal cancer (mCRC) for whom both plasma and tissue samples were available, the kappa coefficient (a measure of acceptable concordance) between ctDNA RAS mutation detection and tissue-based analysis was 0.71, just over the minimum 0.7, and the accuracy of the liquid biopsy sampling was 85.2%, reported Pierre Laurent-Puig, MD, PhD, of Sorbonne University in Paris, and his colleagues.

“[E]ven if our results are limited to the techniques used with their analytic sensitivity, we show here for the first time in a prospective study an excellent concordance between plasma and tumor RAS mutation status in metastatic colorectal cancer patients, especially those with liver metastases. These results validate the routine use of plasma RAS analysis in patients with colorectal cancer and liver metastases,” they wrote. The report was published in Annals of Oncology.

The investigators found that ctDNA was more likely to yield inconclusive results in patients without liver metastases. In patients with liver metastases, the accuracy of the liquid biopsy using next-generation sequencing (NGS) alone to detect RAS mutations was 93.5%, and when detection of methylated biomarkers was added in, the accuracy was 97%.

In the AGEO RASANC prospective multicenter study, the investigators prospectively collected plasma samples from patients with mCRC and sent them to a central lab for analysis by NGS with the colon/lung cancer V2 Ampliseq panel and with digital polymerase chain reaction dPCR for genes associated with DNA methylation (WIF1 and NPY).

Matched tissue samples from the same patients were analyzed locally according to routine practice.

As noted before, the kappa coefficient was 0.71, indicating that agreement between the tests was at least 70% better than by chance alone.

In 329 patients who had detectable ctDNA, defined as at least one mutation or one methylated biomarker, the kappa coefficient rose to 89% and the accuracy to 94.8%.

Also as noted, in the 293 patients with liver metastases, the accuracy improved to close to 100% with both NGS and methylated biomarker detection.

“Based solely on the plasma analysis using our prespecified analysis, 14 patients would have received ineffective and potentially deleterious anti-EGFR therapy. All were considered as truly RAS wild-type in their plasma because of the presence of other mutations detected by NGS and/or a positive methylation assay,” the researchers wrote.

The lack of sensitivity of ctDNA in these patients may have been due to the fact that the fraction of mutated alleles in these patients was lower than in patients for whom both plasma and tissue analysis were negative for RAS mutations. All of these patients had early metastases, which could explain why the sensitivity of the plasma assay was lower than in patients with advanced-stage disease, they said.

“On the contrary detection of RAS mutations in plasma but not in tumor cells could exclude some patients from potentially effective anti-EGFR therapy,” they added. They identified eight patients with plasma-positive, tissue-negative discordance, which could be due to errors in tissue sampling due to heterogeneity of mutations within tissues, or to a lack of sensitivity of RAS mutation detection in tissues.

The trial was sponsored by AGEO and supported by a grant from Merck Serono. Dr. Laurent-Puig disclosed grants from AGEO and personal fees from Merck Serono and other companies. Multiple coauthors reported fees from Merck Serono and others.

SOURCE: Laurent-Puig P et al. Ann Oncol. 2018 Feb 9. doi: 10.1093/annonc/mdy061/4846852.

For identifying patients with metastatic colorectal cancer who might benefit from therapy with drugs targeted against the epidermal growth factor receptor (EGFR), analysis of plasma for circulating tumor DNA – aka “liquid biopsy” – is about as capable as and considerably faster than tissue analysis of RAS mutational status, investigators contend.

Among 412 chemotherapy-naive patients with metastatic colorectal cancer (mCRC) for whom both plasma and tissue samples were available, the kappa coefficient (a measure of acceptable concordance) between ctDNA RAS mutation detection and tissue-based analysis was 0.71, just over the minimum 0.7, and the accuracy of the liquid biopsy sampling was 85.2%, reported Pierre Laurent-Puig, MD, PhD, of Sorbonne University in Paris, and his colleagues.

“[E]ven if our results are limited to the techniques used with their analytic sensitivity, we show here for the first time in a prospective study an excellent concordance between plasma and tumor RAS mutation status in metastatic colorectal cancer patients, especially those with liver metastases. These results validate the routine use of plasma RAS analysis in patients with colorectal cancer and liver metastases,” they wrote. The report was published in Annals of Oncology.

The investigators found that ctDNA was more likely to yield inconclusive results in patients without liver metastases. In patients with liver metastases, the accuracy of the liquid biopsy using next-generation sequencing (NGS) alone to detect RAS mutations was 93.5%, and when detection of methylated biomarkers was added in, the accuracy was 97%.

In the AGEO RASANC prospective multicenter study, the investigators prospectively collected plasma samples from patients with mCRC and sent them to a central lab for analysis by NGS with the colon/lung cancer V2 Ampliseq panel and with digital polymerase chain reaction dPCR for genes associated with DNA methylation (WIF1 and NPY).

Matched tissue samples from the same patients were analyzed locally according to routine practice.

As noted before, the kappa coefficient was 0.71, indicating that agreement between the tests was at least 70% better than by chance alone.

In 329 patients who had detectable ctDNA, defined as at least one mutation or one methylated biomarker, the kappa coefficient rose to 89% and the accuracy to 94.8%.

Also as noted, in the 293 patients with liver metastases, the accuracy improved to close to 100% with both NGS and methylated biomarker detection.

“Based solely on the plasma analysis using our prespecified analysis, 14 patients would have received ineffective and potentially deleterious anti-EGFR therapy. All were considered as truly RAS wild-type in their plasma because of the presence of other mutations detected by NGS and/or a positive methylation assay,” the researchers wrote.

The lack of sensitivity of ctDNA in these patients may have been due to the fact that the fraction of mutated alleles in these patients was lower than in patients for whom both plasma and tissue analysis were negative for RAS mutations. All of these patients had early metastases, which could explain why the sensitivity of the plasma assay was lower than in patients with advanced-stage disease, they said.

“On the contrary detection of RAS mutations in plasma but not in tumor cells could exclude some patients from potentially effective anti-EGFR therapy,” they added. They identified eight patients with plasma-positive, tissue-negative discordance, which could be due to errors in tissue sampling due to heterogeneity of mutations within tissues, or to a lack of sensitivity of RAS mutation detection in tissues.

The trial was sponsored by AGEO and supported by a grant from Merck Serono. Dr. Laurent-Puig disclosed grants from AGEO and personal fees from Merck Serono and other companies. Multiple coauthors reported fees from Merck Serono and others.

SOURCE: Laurent-Puig P et al. Ann Oncol. 2018 Feb 9. doi: 10.1093/annonc/mdy061/4846852.