A group of professional societies has released a draft of a clinical practice guideline on the use of molecular marker testing for patients with primary or metastatic colorectal carcinoma. It is likely that this would help clinicians to decide for molecular testing in Colorectal cancers.
Highlights of Recommendations and Expert Consensus
Recommendations for colorectal cancer molecular marker tests that should be performed include 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 MSI-H with loss of MLH1.)
Expert consensus opinion regarding the most appropriate sample for colorectal cancer molecular marker testing includes the following:
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.