We intend to demonstrate that the prognosis of MSI-H GC patients after D2 radical gastrectomy receiving PD-1 monoclonal antibody immunotherapy would be better than that with standard postoperative adjuvant chemotherapy and follow-up observation.
Approximately 5% to 10% of gastric cancers have MSI-H/dMMR. According to the results of retrospective analysis of CLASSIC and MAGIC, MSI-H/dMMR was a good prognosis and potential negative predictor of adjuvant chemotherapy for resectable gastric cancer. GC patients with MSI-H/dMMR were relatively insensitive to chemotherapy. The prognosis of these patients receiving routine postoperative adjuvant chemotherapy was worse than that with surgery alone. However, these patients were sensitive to immunotherapy. MSI-H/dMMR is one of the most important biomarkers to predict the efficacy of immunotherapy for GC. In this study, patients with MSI-H locally advanced gastric adenocarcinoma after radical surgery with D2 dissection would be randomly treated with conventional adjuvant chemotherapy, PD-1 monoclonal antibody immunotherapy or follow-up observation. We intend to demonstrate that the prognosis of MSI-H GC patients after D2 radical gastrectomy receiving PD-1 monoclonal antibody immunotherapy would be better than that with standard postoperative adjuvant chemotherapy and follow-up observation.