A comprehensive literature analysis of 2740 patients with melanoma, NSCLC, RCC, and urothelial carcinoma from 19 eligible studies who were treated with ICIs, including anti-PD-1/PD-L1 inhibitors and/or anti-CTLA-4 inhibitors, has revealed that antibiotics use are inversely associated with OS and PFS in cancer patients [136]. This evidence concerns the gene PDCD1 and melanoma.