PDCD1 and colorectal carcinoma: Although systematic therapies, such as fluorouracil-based chemotherapy, cetuximab, bevacizumab, and other targeted therapies, as well as programmed cell death protein 1 (PD-1) inhibitors, have achieved survival benefits (to some extent) in advanced CRC patients, their 5-year survival rate is only 14% (5, 6).