SHR-1701 With or Without Apatinib in Combination With Chemotherapy as Neoadjuvant Therapy for Gastric Cancer

Inclusion Criteria: 1. Patients voluntarily participate in this study and provide signed informed consent; 2. Age ≥18 years old; 3. Pathologically confirmed gastric adenocarcinoma or gastroesophageal junction adenocarcinoma (Siewert Type II and Type III adenocarcinoma are permitted); 4. Clinically staged as T3-4aN+M0 by CT or MRI (per AJCC 8th edition), deemed resectable 5. No prior antitumor therapy (e.g., surgery, radiotherapy, chemotherapy, targeted therapy, immunotherapy, etc.); 6. Plan to proceed to surgery after completion of neoadjuvant therapy; 7. Able to swallow tablets normally; 8. Has an Eastern Cooperative Oncology Group (ECOG) performance status score of 0 to 1. 9. Estimated life expectancy ≥12 months; 10. Has adequate organ function. 11. Female subjects of childbearing potential must have a negative serum pregnancy test within 72 hours prior to the first dose and must agree to use a highly effective method of contraception during the study and for 3 months after the last dose of SHR-1701, or 8 weeks after apatinib, or 6 months after chemotherapy (whichever is longer). Male subjects with partners of childbearing potential must be surgically sterile or agree to use a highly effective method of contraception during the study and for 3 months after the last dose of SHR-1701, or 8 weeks after apatinib, or 3 months after chemotherapy (whichever is longer), and must not donate sperm during the study. Exclusion Criteria: 1. Known HER2 positive 2. Need transthoracic surgical approach Based on the investigator's judgment 3. Known peritoneal metastasis or positive peritoneal cytology (CY1P0) or T4b (according to AJCC 8th edition); 4 Presence of unresectable factors, including unresectability due to tumor-related reasons, contraindications to surgery, or refusal of surgery; 5\. Previous or concurrent malignancies, except for cured basal cell carcinoma of skin, carcinoma in situ of cervix, and carcinoma in situ of breast; 6. Uncontrolled hypertension ( systolic ≥140 mmHg or diastolic ≥90 mmHg despite antihypertensive therapy)； 7. Known hypersensitivity to any of the study drugs or excipients; 8. Known hereditary or acquired bleeding and thrombotic tendencies (e.g. hemophiliacs, coagulation disorders, thrombocytopenia, etc.); 9. Congenital or acquired immune deficiency (e.g. HIV infected)