PDCD1 and colorectal carcinoma: found that patients with CRC and a deficient DNA mismatch repair (MMR) (dMMR) or high microsatellite instability (MSI) (MSI-H) benefit from ICI treatment in 2015 (10), ICIs such as programmed cell death 1/programmed cell death 1 ligand (PD-1/PD-L1) inhibitors and cytotoxic T lymphocyte (CTL) antigen 4 (CTLA4) inhibitors have been utilized to treat patients with CRC.