Neoadjuvant Immunotherapy for Resectable Gastric Cancer

Inclusion Criteria:

1. Aged 18-70 years old, both genders, histologically documented gastric cancer.
2. Newly diagnosed locally advanced, potentially resectable disease without any prior antitumor treatment
3. clinically diagnosed stage T3-4bN+M0 according to ultrasound endoscopy or enhanced CT/MRI scan.
4. Eligible and reasonably suitable for potentially curative resection
5. Written (signed) informed consent.
6. Pathological tissue available
7. ECOG: 0-1.
8. Adequate organ function.
9. Willingness to provide blood and tissue samples for research purposes.
10. Good compliance with the study procedures, including lab and auxiliary examination and treatment.
11. Female patients should not be pregnant or breast feeding.
12. Agree to take contraception measures during treatment and in 120 days after last dose of SHR-1210.
13. Life expectancy of at least 6 months.

Exclusion Criteria:

1. Patients with distant metastasis.
2. History of chemotherapy, radiation, immunotherapy, or radical resection of gastric cancer.
3. patients with active autoimmune disease or history of refractory autoimmune disease.
4. patients with active malignant tumor in recent 2 years, except the tumor studied in this research or cured locally tumor like resected basal cell or squamous cell skin cancer, superficial bladder cancer, cervical carcinoma in situ.
5. uncontrollable pleural effusion, pericardial effusion, or ascites in 2 weeks before recruitment.
6. patients who have digestive tract bleeding in 2 weeks before recruitment or with high risk of bleeding.
7. perforation / fistula of GI tract in 6 months before recruitment.
8. pulmonary disease history: interstitial pulmonary disease, non-infective pneumonitis, pulmonary fibrosis, acute pulmonary disease.
9. uncontrollable systemic diseases, including diabetes, hypertension etc.
10. severe chronic or active infections in need of systemic antibacterial, antifungal, or antiviral treatment, including TB or HIV, etc.
11. patients with untreated chronic hepatitis B or HBV DNA over 500 IU/ml or positive HCV RNA.
12. patients with any cardiovascular risk factors below: （1）cardiac chest pain occurring in 28 days before recruitment, defined as moderate pain that limits daily activity.

（2）pulmonary embolism with symptoms occurring in 28 days before recruitment. （3）acute myocardial infarction occurring in 6 months before recruitment. （4）any history of heart failure reaching grade 3/4 of NYHA in 6 months before recruitment.

（5）ventricular arrhythmias of Grade 2 or grater in 6 months before recruitment, or accompanied by supraventricular tachyarrhythmias requiring medical treatment.

（6）cerebrovascular accident within 6 months before recruitment. 14. patients with peripheral neuropathy NCI CTC AE grade 1, except those with only deep tendon reflex disappearing.

15\. moderate or severe renal injury \[creatinine clearance rate≤50 ml/min (according to Cockcroft \& Gault equation)\], or Scr\>ULN.

16\. dipyrimidine dehydrogenase (DPD) deficiency. 17. allergic to any drug in this study. 18. history of allogeneic stem cell transplantation or organ transplantation. 19. use of steroids (dosage\>10mg/d prednisone) or other systemic immune suppressive therapy in 14 days before recruitment, except patients treated with regimens below: a. steroids for hormone replacement (dosage\>10mg/d prednisone); b. steroids for local application with little systemic absorption; c. short -term (≤ 7 days) steroids for preventing allergy or vomiting.

20\. vaccinated with live vaccine in 4 weeks before recruitment. 21. for patients with uncontrolled epilepsy, CNS diseases or history of mental disorder, researchers should evaluate whether their diseases will impede their signing of informed consent or compliance of treatment.

22\. existing of potential situation which will impede drug administration or affect toxicity analysis or alcohol/ drug abuse.