CAP, AMP Among Groups Jointly Issuing Colorectal Cancer Molecular Testing Draft Recommendations

NEW YORK (GenomeWeb) – Several oncology and pathology groups have jointly issued draft recommendations for labs regarding analysis of colorectal cancer patients' samples for certain prognostic and predictive molecular markers.

The draft document, issued by the American Society for Clinical Pathology, the College of American Pathologists, the Association for Molecular Pathology, and the American Society of Clinical Oncology, is available for public comment until April 22.

Echoing current treatment guidelines, the groups also recommended labs perform RAS mutational testing for colorectal cancer patients considering anti-EGFR treatment. Additionally, the groups recommended BRAF V600 mutational analysis with deficient mismatch repair (dMMR) or microsatellite instability (MSI) testing for prognostic stratification of colorectal cancer patients with metastatic disease. But the groups don't yet back BRAF V600 mutation testing as a predictive test to assess response to EGFR inhibitors, citing insufficient evidence.

Moreover, dMMR or MSI testing should be given to all colorectal cancer patients and for identifying Lynch syndrome patients, according to the draft recommendations. The groups don't support PIK3CA mutational testing or PTEN analysis for guiding treatment decisions outside of a clinical trial setting.

According to the guidelines, formalin-fixed paraffin-embedded tissue from the primary or metastatic tumor is acceptable for analysis. Labs must use validated testing methods, in line with best lab practices. "In particular, laboratories performing colorectal carcinoma molecular marker testing must participate in formal proficiency testing programs, if available, or an alternative proficiency assurance activity," the draft guidance states.

CAP runs proficiency testing programs for MSI testing, as well as BRAF and KRAS mutation testing. The organization has been running the MSI proficiency testing survey for 10 years, which includes 128 participating labs, while the BRAF testing program includes more than 200 labs and the KRAS testing program involves just under 250 labs.

There is greater than 90 percent consensus among labs partaking in these proficiency testing programs, NorthShore University HealthSystem's Jan Nowak said at a recent meeting of the Centers for Medicare & Medicaid Services' Medicare Evidence Development and Coverage Advisory Committee.

The committee met last week to evaluate the evidence backing KRAS, BRAF, MSI and MLHI promoter methylation testing for assessing prognosis in colorectal cancer, in addition to a number of other cancer-linked markers. After reviewing the data gathered from a technological assessment conducted in late 2013, they voted that only MSI testing passed muster for analytical/clinical validity and for impacting health outcomes, while BRAF and KRAS testing met only the analytical/clinical validity threshold. 

In contrast, the latest draft guidelines from ASCP/CAP/AMP/ASCO suggested labs prioritize colorectal cancer patients' tumor samples for broader RAS mutation testing, as well as for BRAF mutations, dMMR, and MSI. Furthermore, according to the draft recommendations, labs should employ testing methods so that mutations may be detected in specimens with at least 5 percent mutant allele frequency, after factoring in the analytical sensitivity of the assay and tumor enrichment.

Finally, the groups provided timelines for analysis and reporting results. For send-out samples, 90 percent of samples should be mailed out in three working days. Similarly, labs should report results for 90 percent of tests within 10 working days, according to the recommendations.

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