Paradigms on Immunotherapy Combinations with Chemotherapy

Checkpoint inhibitors are being added to standard-of-care chemotherapy in multiple clinical trials. Success has been reported in non-small and small cell lung carcinomas and urothelial, head and neck, gastric, and esophageal cancers, and promising results are already available in triple-negative breast and pancreatic malignancies. The potential mechanisms of synergy include immunogenic tumor cell death, antiangiogenesis, selective depletion of myeloid immunosuppressive cells, and lymphopenia, which reduces regulatory T cells and makes room for proliferation of effector T cells. However, chemotherapy regimens have not been optimized for such combinations, perhaps explaining some recent clinical trial disappointments. Approaches to make the most of chemoimmunotherapy include neoadjuvant and adjuvant schemes. Immunotherapy of cancer based on PD-1/PD-L1 blockade has prompted a revolution in cancer clinical management. Evidence in phase III clinical trials already supports combinations of immunotherapy with standard-of-care chemotherapy for a number of malignant diseases. This review focuses on such evidence and provides an overview of the potential synergistic mechanisms of action and the opportunities to optimize chemoimmunotherapy regimens.