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A multitude of recent clinical trials have indicated that expanded RAS testing is more effective than traditional KRAS testing for patients with colorectal cancer (CRC). As a result of these findings, the number of patients with CRC who are eligible for EGFR inhibitors has been reduced to approximately 40%. However, only 25% to 33% of patients are actually receiving these treatments, points out Alan P. Venook, MD.
Outside of testing, the appearance of a treatment-related skin rash could indicate whether or not a patient is responding to treatment with an EGFR inhibitor, Venook notes. If a rash has not developed, it may be safe to discontinue therapy or retest using the expanded criteria for patients who were already on EGFR inhibitors before expanded testing was available.
Putting this new testing strategy into practice requires multidisciplinary collaboration, since pathologists generally order the tests, notes John L. Marshall, MD. The current reflex for testing is KRAS exon 2 codon 12 and 13 alone, which should be expanded to include KRAS exon 3 and 4 and NRAS exon 2 and 3 mutations.
Reimbursement for expanded testing represents a possible challenge in some settings, Venook believes. Additionally, there is a level of education require in order to accurately interpret the expanded results.