Several studies investigated the association between genetic polymorphisms of PD-1 and PD-L1 genes and the risk of various cancers, but the finding are still inconclusive [5,6,7,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52]. The gene discussed is PDCD1; the disease is cancer.