Treatment sequencing of metastatic colorectal cancer based on primary tumor location

Colorectal cancer is a heterogeneous disease with various clinical, molecular, and embryological differences related to the origin of the tumor from the right or left colon. Recent studies have demonstrated that tumor sidedness has both a prognostic and predictive value in metastatic colorectal cancer . Patients whose primary tumor originates from the left side of the colon and whose tumor's genome encodes wild-type RAS and BRAF should be offered cetuximab or panitumumab in the first-line treatment of metastatic disease or in subsequent lines. For tumors originating from the right side of the colon, anti-angiogenic treatment, particularly bevacizumab, is an option for this poor prognostic group until better options become available. Specifically, an aggressive initial approach with FOLFOXIRI plus bevacizumab is a treatment option in right-sided tumors under investigation. This report reviews the available data for the treatment of metastatic colorectal cancer according to the location of the primary tumor and proposes the optimal treatment sequencing strategy incorporating the site of origin of the tumor and molecular information into the decision-making process.