This study objectively analyzes the safety and survival evaluation of perioperative immunotherapy combined with chemotherapy in locally advanced gastric cancer patients through a prospective randomized controlled trial research method; By comparing the pathological response rate, disease-free survival rate, and incidence of adverse events between the combination therapy and chemotherapy alone group, we aim to verify the efficacy and safety of tirelizumab combined with SOX/XELOX chemotherapy in disease control of locally advanced gastric cancer patients, laying the foundation and providing a basis for large-scale multicenter clinical research.

Inclusion Criteria:

• The subjects voluntarily joined this study and signed an informed consent form
• Locally advanced gastric or gastroesophageal junction adenocarcinoma confirmed by pathology or histology as HER-2 negative (cT2-4N+M0 Phase II-III)
• The primary lesion can be surgically removed, and the patient is willing to receive surgical treatment
• There are measurable solid tumors (efficacy evaluation standard: RECIST 1.1)
• Tumor evaluation should be conducted through CT scanning or MRI within 28 days before treatment
• ECOG score 0-1
• Life expectancy ≥ 12 months.

Exclusion Criteria:

• Preoperative imaging examination indicates distant or peritoneal metastasis in patients
• Subjects with any known active autoimmune disease
• Serious cardiovascular disease
• The serum of the subjects tested positive for HIV
• Active hepatitis B (HbsAg positive and HBV-DNA ≥ 10 ^ 3copies/mL) or active hepatitis C (HCV antibody positive and HCV-DNA positive, requiring antiviral treatment at the same time)
• Known subjects with previous allergies to macromolecular protein formulations/monoclonal antibody components, or other contraindications to immunotherapy or chemotherapy
• Have a history of alcohol, drug, or substance abuse
• Individuals with a clear history of neurological or mental disorders, such as epilepsy, dementia, and poor compliance