Fast Five Quiz: Colorectal Cancer Practice Essentials

Elwyn C. Cabebe, MD


June 17, 2022

Treatment of metastatic colorectal cancer is increasingly guided by molecular testing of the tumor. The ASCP, CAP, AMP, and the ASCO have issued evidence-based guidelines on colorectal cancer molecular testing. Recommendations include:

  • RAS mutational testing of colorectal carcinoma tissue should be performed for patients who are being considered for anti-EGFR therapy; this analysis must include KRAS and NRAS codons 12 and 13 of exon 2, 59 and 61 of exon 3, and 117 and 146 of exon 4 ("expanded" or "extended" RAS).

  • BRAF V600 mutational analysis should be performed in conjunction with dMMR/MSI testing for prognostic stratification.

  • dMMR/MSI testing must be performed in all patients with colorectal cancer for prognostic stratification and identification of patients with Lynch syndrome. BRAF mutation testing for Lynch syndrome is not needed if there is no high MSI with loss of MLH1.

  • Molecular marker testing (KRAS, extended RAS, BRAF, and dMMR/MSI) of the primary colorectal carcinoma tissue is acceptable; if metastatic tissue is available, that is also acceptable and is preferable in patients with metastatic disease.

  • Formalin-fixed, paraffin-embedded tissue is an acceptable specimen; use of other specimens will require additional adequate validation, as would any changes in tissue-processing protocols.

Learn more about molecular testing in colon cancer workup.


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