Assessing Real-World Biomarker Testing Rates In Metastatic Colon Cancer

209 Background: Despite national guideline recommendations for universal biomarker testing (KRAS, NRAS, BRAF, and mismatch repair/microsatellite instability [MMR/MSI]) in all patients with metastatic colorectal cancer (mCRC), little is known regarding adherence to these recommendations in the community. Methods: We evaluated 20,333 patients aged >18 years with mCRC diagnosed between 1/1/2013-12/27/18 from the nationwide de-identified Flatiron Health electronic health record-derived database. Changes in rates of biomarker testing based upon chart abstraction according to date of mCRC diagnosis were assessed in patients with ≥ 6 months of follow-up using Cochran-Armitage trend tests. We also assessed whether testing differed by patient characteristics using chi-square tests. Results: Biomarker testing rates increased between 2013 and 2018 (15.3 to 65.7% for NRAS, 23.9 to 56.6% for BRAF, and 34 to 76.6% for MMR, all p < 0.0001). There was no change in rate of KRAS testing (63.8 to 68.3% p= 0.1695) over this period of time. Univariate analysis showed that patients with, worse performance status, and Medicare/Medicaid insurance were less likely to be tested (for all variables, p <0.0001). There were no meaningful differences in testing rates by tumor sidedness, race, gender, or initial stage. Conclusions: In mCRC, adoption of guideline-driven recommendations for NRAS, BRAF and MMR/MSI testing increased significantly between 2013-2018. Adoption of BRAF and NRAS testing has neared the rate of KRAS testing. Interpretation of overall testing rates must recognize potential for missing biomarker test information for care not captured within the Flatiron network. Further study is required to characterize the magnitude of and reasons for absent biomarker testing among patients with metastatic colorectal cancer.