Abstract: Gastric cancer has high morbidity and mortality, and limited treatment options for advanced cancer. In recent years, with the advent of targeted drugs (including VEGFR-2 antagonists, anti-HER-2 antibodies) and immunotherapeutics (such as anti-CTLA-4 antibodies, anti-PD-1/PD-L1 antibodies), the efficacy of advanced gastric cancer has been increased. Currently, the clinical data of PD-1 and its ligand PD-L1 inhibitors have achieved phased success, but which factors affect the efficacy of PD-1/PD-L1 immune checkpoint inhibitors immunotherapy, and how to select the benefited patient population and establish the prognosis evaluation system are the urgent problems to be solved. Therefore, this review elaborated the factors affecting the immunotherapy effects of PD-1/PD-L1 inhibitors from the aspects of systemic chemotherapy, intestinal microbiota, MSI, Hp infection, Epstein-Barr virus, TMB, and tumor infiltrating lymphocytes, in order to provide new ideas for clinical work.

Key words: gastric cancer, immune checkpoint, tumor immune microenvironment, prognosis