PDCD1 and colorectal carcinoma: Thereafter the impressive efficacy and safety of CheckMate-142 (23) and KEYNOTE-177 (16) in the treatment of dMMR/MSI-H mCRC promoted the Food and Drug Administration (FDA) ‘s approval of pembrolizumab, a programmed cell death-1 (PD-1) inhibitor, as the first-line treatment for MSI-H advanced CRC.