PDCD1 and colorectal carcinoma: In advanced CRC, a phase Ib trial demonstrated that a PD-1 inhibitor plus chemotherapy obtained a DCR of 43.3% (16); additionally, a PD-1 inhibitor showed favorable efficacy in patients with metastatic, microsatellite instability-high/mismatch repair-deficient (MSI-H/dMMR) CRC (17).