What are the American Society for Clinical Pathology, the College of American Pathologists (CAP), the Association for Molecular Pathology, and the American Society of Clinical Oncology (ASCO) evidence-based guidelines on colorectal cancer molecular test..

Updated: Apr 15, 2020
  • Author: Tomislav Dragovich, MD, PhD; Chief Editor: N Joseph Espat, MD, MS, FACS  more...
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Answer

Treatment of metastatic colorectal cancer is increasingly guided by molecular testing of the tumor. The American Society for Clinical Pathology, the College of American Pathologists (CAP), the Association for Molecular Pathology, and the American Society of Clinical Oncology (ASCO) have issued evidence-based guidelines on colorectal cancer molecular testing. [65]  Among the recommendations are the following:

  • 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, 13 of exon 2; 59, 61 of exon 3; and 117 and 146 of exon 4 ("expanded" or "extended" RAS)

  • BRAF V600 mutational analysis should be done in conjunction with deficient mismatch repair (dMMR)/microsatellite instability (MSI) testing for prognostic stratification

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

  • Molecular marker testing (KRAS, extended RASBRAF, 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


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