PDCD1 and cancer: A Phase II trial characterizing the role of anti-PD1 immunotherapy in patients with colorectal cancers with high microsatellite instability (MSI) found that patients with colorectal cancers that have deficient mismatch repair mechanism had significantly improved responses (40%) and immune-related progression-free survival rates (78%) than those who had cancers with an intact mismatch repair (0% and 11% respectively).