PDCD1 and colorectal carcinoma: In addition to radiochemotherapy and surgery, the use of immune checkpoint inhibitors (ICIs) in immunotherapy in recent years has provided a new treatment strategy for patients with advanced or refractory CRC, especially targeted therapy involving the important immune checkpoint proteins (ICPs) programmed death protein-1 (PD-1) and its ligand programmed death-ligand 1 (PD-L1).