The keywords used for the search were “colorectal neoplasms”, “colorectal cancer”, “colorectal tumors”, “colorectal carcinoma”, “immune checkpoint inhibitor”, “PD-1 Inhibitors”, “programmed cell death protein 1 inhibitor”, “PD-L1 Inhibitors”, and “Programmed Death-Ligand 1 Inhibitors”. This evidence concerns the gene PDCD1 and colorectal cancer.