Immune checkpoint inhibitors (ICIs) are monoclonal antibodies that have revolutionized the treatment landscape of various cancers by targeting cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4), programmed cell death protein-1 (PD-1), and programmed death-ligand 1 (PD-L1) [1]. This evidence concerns the gene PDCD1 and cancer.