To explore the safety and efficacy of local advanced stomach cancer patients receiving new complementary treatment of PD-1 monoantiotherapy before surgery

Inclusion Criteria:

1. Histologically proven adenocarcinoma of the stomach, PD-L1+(CPS≥1).
2. Clinical cT3-4a/N+M0 disease, confirmed by upper gastrointestinal endoscopy and abdominal computed tomography (CT) and laparoscopy.
3. The gastric tumors are macroscopically resectable by distal gastrectomy with D2 lymph node dissection, and R0 or R1 resection can be achieved.
4. No bulky lymph node metastasis is detected by abdominal CT.
5. No pleural effusion, no ascites exceeding the pelvis and no metastasis to the peritoneum, liver or other distant organs are confirmed by abdominal pelvic CT.
6. No clinically apparent distant metastasis.
7. Karnofsky performance status ≥70%.
8. Sufficient oral intake.
9. No previous treatment with chemotherapy or radiation therapy for any tumors.
10. No previous surgery for the present disease.
11. Sufficient organ function, as evaluated by laboratory tests 7 days or more after the date when the anticancer drugs were given. When patients are recovering from myelosuppression,the revised criteria are shown in parentheses. White blood cell count≥3000/mm3 (2000/mm3) Platelet count≥10.0*104/mm3 (5.0*104/mm3) Aspartate aminotransferase≤100 IU/l Alanine aminotransferase≤100 IU/l Total bilirubin≤2.0 mg/dl Serum creatinine≤1.5 mg/dl
12. No need for emergency surgery due to bleeding or perforation of the primary tumor.
13. No mechanical obstruction.
14. Written informed consent.

Exclusion Criteria:

1. Past history of upper abdominal surgery.
2. Past history of surgery for the gastrointestinal tract.
3. Body mass index exceeding 30 kg/m2.