Of 310 cancer patients treated with ICIs at Coltea Clinical Hospital, Bucharest, Romania, over a period of 5 years, we identified 1 case of breast cancer, 3 of cancer of unknown primary, 12 of renal cancer, 10 of urothelial cancer, 42 of malignant melanoma, 91 of head and neck cancer and 151 of lung cancer, respectively, treated with PD-1 inhibitor (nivolumab—142 patients, pembrolizumab—146 patients), PD-L1 inhibitor (atezolizumab—10 patients, durvalumab—2 patients, avelumab—1 patient) and CTLA-4 antibody (ipilimumab—9 patients). The gene discussed is CTLA4; the disease is renal carcinoma.