PDCD1 and adenocarcinoma: Recently, based on the results of several clinical trials (e.g., CheckMate 649, KEYNOTE-859, ORIENT-16, and RATIONALE-305), anti-programmed cell death protein-1 (PD-1) plus chemotherapy has become the standard first-line treatment for HER2-negative, unresectable, locally advanced or metastatic gastric or gastroesophageal junction (G/GEJ) adenocarcinomas.