KRAS exons 3, 4
NRAS exons 2, 3, & 4
This assay uses pyrosequencing technology to detect clinically relevant mutations in KRAS codons 59, 61, 117 and 146; and in NRAS codons 12, 13, 59, 61, 117, and 146. See KRAS cobas® IVD (the Roche cobas® KRAS Mutation Test) for testing to detect the most common missense point mutations in codon 12 and 13 of KRAS exon 2.
RAS proteins are involved in the EGFR signal transduction pathway. Mutated RAS protein is constitutively activated and tumors carrying these activating mutations have been shown to be resistant to anti-EGFR directed therapy. According to joint guidelines recently issued by ASCP, CAP, AMP and ASCO (see reference below), all patients with colorectal carcinoma being considered for anti-EGFR therapy must undergo RAS mutation testing to determine eligibility. RAS mutation analysis should include KRAS codons 12 and 13 (evaluated by the FDA-approved cobas assay; see KRAS cobas IVD) as well as “extended” RAS testing targeting KRAS codons 59, 61, 117, and 146; and NRAS codons 12, 13, 59, 61, 117, and 146.
For colorectal carcinoma patients, PhenoPath recommends ordering RAS mutation testing in a reflexive manner, starting with this FDA-approved cobas® KRAS Mutation Test to test for KRAS exon 2 mutations, followed by extended RAS mutation testing if a KRAS exon 2 mutation is not detected (see Extended RAS Panel).
REFERENCE: Sepulveda AR, et al. Molecular Biomarkers for the Evaluation of Colorectal Cancer: Guideline From the American Society for Clinical Pathology, College of American Pathologists, Association for Molecular Pathology, and American Society of Clinical Oncology. J Mol Diagn 2017 19(2):187225.
Organ: Colon & Other GI
CPT Code(s): 81311, 81276 (88381 may apply)
Turnaround Time: Within 5-8 business days of receipt
Schedule: Tuesday and Thursday
Formalin-fixed, paraffin-embedded (FFPE) tissue block (preferred) or unstained slides (10 slides are usually sufficient)