Clinical Study of Low-dose Interval Radiotherapy Combined With Tirelizumab and SOX Chemotherapy Neoadjuvant Therapy for Locally Advanced Gastric/Gastroesophageal Junction Adenocarcinoma

Inclusion Criteria: * Patients voluntarily participated in the study and signed informed consent with good compliance and follow-up; * Adenocarcinoma of the gastric/gastroesophageal junction confirmed by endoscopic pathology (tumor located in the lesser bend of the stomach other than pylorus or the gastroesophageal junction) (Note: Pathology in other hospitals must be consulted by our hospital); * Patients with cT4N+M0 AJCC stage 8 combined with endoscopic, CT, MRI, or PETCT findings; * Age ≥18 years, ≤75 years, male and female; * ECOG PS score 0-1; * Presence of measurable and/or unmeasurable lesions as defined by the efficacy evaluation criteria for solid tumors (Recist 1.1); * Has not received any prior systemic antitumor therapy (including but not limited to systemic chemotherapy, radiotherapy, molecular targeted drug therapy, immunotherapy, biotherapy, topical therapy, or other investigational therapeutic drugs; * The functions of vital organs meet the following requirements (no blood components and cell growth factors are allowed to be used 2 weeks before screening) : Neutrophil absolute count (ANC) ≥ 1.5×10 9/L; Platelets ≥100×10 9/L; Hemoglobin ≥9g/dL; Serum albumin ≥2.8g/dL; Total bilirubin ≤ 1.5 ×ULN, ALT, AST and/or AKP≤2.5 ×ULN; serum creatinine ≤1.5 ×ULN or creatinine clearance ≥60mL/min (calculated according to the Cockcroft-Gault formula); International standardized ratio (INR) and activated partial thrombin time (APTT) ≤1.5×ULN (INR can be screened in the exp…