Several polymorphisms in immune-regulatory genes, including PD-1 rs36084323, PD-L1 rs822336 and rs4143815, PD-L1 copy number variation (CNV), FOXP3 rs3761548 and rs2232365, and miR-155 rs767649, have been implicated in cancer susceptibility and prognosis. This evidence concerns the gene PDCD1 and cancer.