Neoadjuvant Immunotherapy Plus Chemotherapy in Borrmann Type 4 and Large Type 3 Gastric Cancer

Inclusion Criteria: * Histologically confirmed gastric adenocarcinoma,cT1-2N+M0 or cT3-4NanyM0; * Males or females, aged 18-70 years; * Gastroscopy and abdominal computed tomography (CT) scan-confirmed typical scirrhous gastric cancer (borrmann type 4) or large type 3 (over 8 cm); * No peritoneal metastasis confirmed by laparoscopic exploration and with cytological examination of peritoneal washing of the Douglas pouch; * ECOG performance status 0 or 1; * Sufficient organ function: * white blood cell count \> 4\*10\^9/L, neutrophil cell count \> 1.5\*10\^9/L, hemoglobin \> 90 g/L, platelet count \> 100\*10\^9 /L * Serum bilirubin ≤ 1.5×upper limit of normal (ULN), AST, ALT ≤ 2.5×ULN * Creatinine ≤ 1.5 ×ULN or serum clearance \> 60 ml/min * INR and aPTT ≤ 1.5 × ULN, only for subjects not receiving anticoagulant therapy;Subjects undergoing coagulation therapy should use a stable dose * No prior anti-tumor therapy; * Have signed informed consent before the beginning of treatment. Exclusion Criteria: * History of another malignancy within the last five years; * Previous cytotoxic chemotherapy, radiotherapy or immunotherapy * Unable to take drugs orally * Allergic to to any drug of the study regimen; * Women who are pregnant or breastfeeding or may be pregnant