PDCD1 and gastric cancer: Immune-checkpoint inhibitors have become the leading immunotherapy approach in the treatment of STAD.3 Programmed cell death 1 (PDCD1, also known as PD-1) and programmed cell death-ligand 1 (PD-L1) inhibitors decrease the size of tumours and prolong the overall survival of a subset of patients with gastric cancer.4,5 Highly unstable microsatellites and mismatch repair defects are important prognostic indicators for tumours.