Total study populations for ICIs (melanoma, NSCLC, HCC, and RCC) and type of ICI interventions (anti-PD-1 [n = 5], anti-CTLA-4 [n = 2], and a combination of anti-PD-1 and anti-CTLA-4 [n = 3]) varied across studies. This evidence concerns the gene PDCD1 and melanoma.