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Testing for mutations in lung cancer is a very important part of practice today and it is now part of official guidelines to do so, according to Lecia V. Sequist, MD, MPH, an associate professor of Medicine at Harvard Medical School and attending physician at Massachusetts General Hospital.
Based on recommendations from CAP and IASLC, all patients with adenocarcinoma or mixed histology with an adenocarcinoma component should be tested, regardless of clinical factors. “At a minimum, one needs to test for EGFR mutations and ALK translocations since there are FDA approved drugs targeting both.
A multiplex test that looks at several mutations makes the most sense because it preserves precious biopsy tissue. ROS mutations can be useful to test for as well, since the drug that targets ALK can be used in ROS-mutant patients. In addition, there are mutations for which there are available targeted therapies in other cancers, such as BRAF.
A question that often comes up is whether to test for KRAS mutations. Although KRAS mutations are present in 30% of patents with adenocarcinoma, no approved targeted therapy exists yet for KRAS-mutant lung cancer. However, Sequist notes that KRAS testing can be helpful since, typically, a lung cancer will have one driver mutation—so identifying a positive KRAS mutation excludes looking for other, rarer drivers.