FMT+SOX+Sintilimab As First-line Treatment for Advanced Gastric Cancer

the investigators plan to initiate a prospective, multicenter, randomized, double-blind, placebo-controlled phase II study, recruiting 198 patients with advanced gastric/gastroesophageal junction adenocarcinoma who have not received prior treatment. Randomly divided into two groups, one group is the group of fecal microbiota transplantation(FMT)+SOX+Sintilimab, and the other group is the group of SOX+Sintilimab. Compare the 2-year OS rates of the two groups to verify whether the addition of FMT to first-line treatment can improve the prognosis of gastric cancer patients.