Prognostic impact of primary tumor site location in metastatic colorectal cancer (mCRC).

578 Background: CRC site is associated with differences in key molecular features that may impact survival in the metastatic (met) setting. We assessed the magnitude of outcome differences in a non-clinical trial scenario and explored how rectum cancer (RC) compares with right- and left-sided (RS and LS) colon tumors. Methods: Retrospective analysis of clinicopathological and molecular data from all mCRC patients (pts) treated at VHIO from January 2010 to June 2015. Targeted mutation (mut) profiling of driver oncogenes was performed by mass spectrometry (MassARRAY, Sequenom) or with next generation sequencing (Amplicon MiSeq, Illumina). Survival after relapse (SAR) was defined as time from diagnosis of met disease to death. Tumor site was categorized as RS (cecum, ascending, hepatic flexure, and transverse), LS (splenic flexure, descending, and sigmoid) or RC. We performed Cox proportional hazards models and adjusted for covariates including number and location of met sites, surgical resection of met lesi...