Primary site and treatment impact in unresectable metastatic colorectal cancer.

Primary site is a prognostic marker in metastatic colorectal cancer, with right colon tumors being associated with more aggressive disease behavior and poorer outcomes. Primary site also appears to predict for outcomes to various treatments, in particular anti-EGFR antibodies. As our understanding and testing of the molecular and biological differences within colorectal cancer increases beyond primary site, this should be integrated into the current treatment algorithm to ensure an individualized patient-centered approach to care.