PDCD1 and neoplasm: For colorectal cancer (CRC), anti-PD-1 and anti-PD-L1 therapy often generates a durable response in patients with mismatch repair-deficient/microsatellite instability high (dMMR/MSI-H) CRC, which is a tumor subtype with high TMB, compared to failure in microsatellite stable (MSS) CRC, which has a significantly lower TMB (239, 240).