Seeing the forest through the trees: A systematic review of the safety and efficacy of combination chemotherapies used in the treatment of metastatic colorectal cancer

Combinations of fluoropyrimidines with oxaliplatin or irinotecan plus a biologic agent are standard treatments for metastatic colorectal cancer (mCRC). Recent approvals of first-line cetuximab, second-line ziv-aflibercept, and regorafenib as salvage therapy have increased the complexity of the treatment armamentarium. To define optimal regimens, we systematically reviewed combination chemotherapy trials (N= 83). Descriptive analyses focusing on fluoropyrimidine formulation, oxaliplatin vs irinotecan combinations, and compatibility with biologics indicated the following: infusional 5-fluorouracil (5-FU) yielded better efficacy and safety than bolus 5-FU. Capecitabine had similar outcomes and better safety than 5-FU with oxaliplatin but not irinotecan. First-line oxaliplatin and irinotecan appeared equivalent. Antiangiogenics, such as bevacizumab and ziv-aflibercept, and epidermal growth factor receptor-targeted monoclonal antibodies cetuximab and panitumumab further improved efficacy. The treatment landscape for mCRC has become complex, and we are approaching individualized therapy based on predictive factors, including KRAS mutational status. Appropriate administration of chemotherapy/biologic combinations is critical.