Left- Versus Right-Side Metastatic Colorectal Cancer: Teasing Out Clinicopathologic Drivers Of Disparity In Survival.

623Background: Patients with metastatic colorectal cancer (mCRC) arising from a right sided colorectal cancer (RC) have an inferior survival versus patients with a left sided colorectal cancer (LC). Previous analyses have suggested that multiple factors contribute. Methods: The Treatment of Recurrent and Advanced Colorectal Cancer (TRACC) Registry has prospectively captured comprehensive data on consecutive mCRC patients since 2009. For this analysis LC were defined as primary tumors at or distal to the splenic flexure and included rectal cancers. We analysed patient, tumor, treatment and outcome data. Results: Of 2306 patients enrolled from July 2009–March 2018, median age 67 years (range 18–100), 1559 (67.6%) had a LC. Patients with a RC were older (median 71 vs 65 years, p u003c 0.001), more likely to be female (50.2% vs 36.9%, p u003c 0.001) and to have a Charlson score ≥ 3 (67.5% vs 54.6%, p u003c 0.001). More common in RC, where tested, were BRAF mutations (22.3% vs 7.2%, p u003c 0.001) and deficient mismatch repai...