When PD-1 inhibitors and CTLA4 inhibitors are used in combination for renal cell carcinoma, colorectal cancer, melanoma, small cell lung cancer (SCLC), and hepatocellular carcinoma, the incidence of colitis is higher for a 3 mg/kg dosage of ipilimumab and a 1 mg/kg dosage of nivolumab than a 1 mg/kg dosage of ipilimumab and a 3 mg/kg dosage of nivolumab [23,24]. This evidence concerns the gene CTLA4 and colitis.