Chemotherapy Sequential Tislelizumab After Radical Resection in Patients With dMMR/MSI-H or POLE/POLD1 Mutations

About 30 patients who underwent radical gastrectomy or enterectomy with gastric adenocarcinoma or esophagogastric junction adenocarcinoma with postoperative pathological stage III or intestinal adenocarcinoma with postoperative pathological stage T1-3N2M0 or T4N+M0(American Joint Committee on Cancer,AJCC 8th Edition Cancer Stage) were scheduled to be enrolled after fully informed and signed informed consent Qualified subjects were selected to receive the standard XELOX or SOX regimen selected by the investigators according to the disease and postoperative pathology of the subjects for 4 cycles, followed by the sequential treatment of monotherapy tislelizumab (200mg,Q3W, IV infusion,4 cycles) starting from 4-6 weeks after surgery, with a maximum of 12 weeks Safety assessments such as ECOG physical examination of vital signs and laboratory tests will be performed regularly during treatment