Efficacy and Safety of Neoadjuvant Sintilimab Plus FLOT Versus Sintilimab Plus SOX Phase II Clinical Trial for Patients With Locally Advanced Gastric Cancer

Inclusion Criteria: * 1\. Age \>=18 years and \<100 years. * 2\. Diagnosed with locally advanced gastric cancer. * 3\. Eastern Cooperative Oncology Group ECOG PS score 0-1. * 4\. adoption of preoperative chemotherapy treatment and PD-1 antibody therapy. * 5\. deficient mismatch repair identified by pathological detection. Exclusion Criteria: * 1\. Locally advanced unable to resect or metastatic tumors. * 2\. Patients with recurrence of residual gastric cancer * 3\. Patients refusing surgical resection after preoperative chemotherapy therapy. * 4\. Have received any anti-tumor therapy such as chemotherapy, radiotherapy, immunotherapy, etc., or have been more than 180 days since the last treatment. * 5\. Patients with confirmed allergy to the study drug and/or its excipients. * 6\. Severe malnutrition and active autoimmune diseases. * 7\. Pregnant or lactating women. * 8\. Patients with medical systemic diseases and psychiatric diseases that are not amenable to chemotherapy. * 9\. Patients with acute infections requiring antibiotic treatment. * 10\. Patients with acute infections requiring antibiotic treatment. * 11\. Patients who are concomitantly receiving other immunotherapy, corticosteroids, and other anticancer therapies during the trial. * 12\. Positive test result for hepatitis B or hepatitis C virus. * 13\. Untreated central nervous system metastatic peripheral neuropathy (\>grade 1). * 14\. History of malignancy within the past 5 years (with the exception of curative, localized cancer). * 15\. Patients who are not expected to achieve R0 resection. * 16\. Weight loss greater than or equal to 20% within 4 weeks before the first dose. * 17\. Patients with multiple factors affecting oral medication. * 18\. Vaccination within 4 weeks prior to the first dose of study drug. * 19\. Patients who have received immune checkpoint inhibitors and develop serious adverse reactions after treatment and need to be permanently disabled. * 20\. The investigator believes that the subject has other serious systemic diseases or other reasons and is not suitable for this clinical study.