Primary site and treatment impact in unresectable metastatic colorectal cancer

IntroductionColorectal cancer is a heterogenous disease, with various clinical and molecular subtypes related to the primary site (left versus right colon) of the original tumor. Primary colon tumor side is both a prognostic and predictive marker in metastatic colorectal cancer.Areas coveredThere is an increasing body of evidence for how primary site may impact treatment decisions in metastatic colorectal cancer. We reviewed the evidence for its prognostic and predictive value.Expert opinionPrimary 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.

Automated summary

Colorectal cancer is a heterogeneous disease with different subtypes related to the primary site. The primary colon tumor side is both a prognostic factor and a predictive marker in metastatic colorectal cancer. This review examines the evidence for its prognostic and predictive value.