Selecting Optimal First-Line Treatment for Microsatellite Stable and Non-Mutated RAS/BRAF Metastatic Colorectal Cancer

Standard frontline treatment of metastatic colorectal cancer (CRC) is cytotoxic chemotherapy plus a biologic agent such as an anti-EGFR monoclonal antibody (cetuximab or panitumumab) or anti-VEGF antibody (bevacizumab). Predictive biomarkers include mismatch repair (MMR) status, and RAS and BRAF mutation status; and important factors in treatment selection include primary tumor location, intent of therapy, and potential toxicity, as well as patient age, comorbidities, and patient preference. To date, single-, double-, or triple-agent cytotoxic chemotherapy all have important roles in appropriately selected patients, with the addition of anti-VEGF or anti-EGFR antibody therapy based on the relevant predictive biomarker. Data indicate that patients with proficient MMR, RAS/BRAF wt mCRC are candidates for an anti-EGFR antibody plus doublet chemotherapy if they have a left-sided primary tumor, or for anti-VEGF (bevacizumab) plus doublet or triplet chemotherapy if they have a right-sided primary tumor. Future studies may provide more predictive biomarkers to further personalize therapy for this heterogeneous disease.