CTLA4 and metastatic malignant neoplasm: As shown in the global, phase III KEYNOTE-177 trial, patients with microsatellite instability-high/mismatch repair deficiency (MSI-H/dMMR) tumors, may benefit from single-agent pembrolizumab.11 PD-1 inhibitors have been approved in a tumor-agnostic manner beyond first-line for treatment of patients with MSI-H/dMMR tumors and can be used in combination with cytotoxic T-lymphocyte-associated protein 4 inhibitors (CTLA-4).12,13 Unfortunately, MSI-H/dMMR tumors constitute only 4% to 5% of metastatic cancers.