Irinotecan Liposome II + 5-FU/LV + Oxaliplatin + Karelizumab in Neoadjuvant Treatment of Gastric Cancer

Inclusion Criteria: 1. age ≥ 18 years and ≤ 75 years; 2. gastric cancer confirmed by histopathology or cytology; 3. critically resectable gastric cancer confirmed by imaging; 4. at least one measurable lesion (according to RECIST v1.1); 5. ECOG score of 0 to 2; 6. expected survival time ≥ 3 months; 7. UGTA1\*1\*28 and UGTA1\*1\*6 genes tested wild-type; 8. bone marrow function: neutrophils (ANC) ≥1.5×10\^9/L, platelets (PLT) ≥100×10\^9/L, hemoglobin (Hb) ≥90g/L, white blood cells (WBC) ≥3.0×10\^9/L; 9. Liver function: alanine aminotransferase (ALT), alanine transaminase (AST), alkaline phosphatase (ALP) ≤2.5×ULN (upper limit of normal), ≤5×ULN in case of liver metastasis; total bilirubin ≤1.5×ULN; 10. renal function: serum creatinine (Cr) ≤1.5×ULN or creatinine clearance ≥60 ml/min (calculated according to Cockroft-Gault), urine protein \<2+; 11. coagulation: international normalized ratio (INR) ≤ 1.5 times upper limit of normal (ULN) and activated partial thromboplastin time (APTT) ≤ 1.5 times upper limit of normal (ULN); 12. be able to understand the circumstances of this study, and the patient and/or legal representative voluntarily agree to participate in this trial and sign the informed consent form. Exclusion Criteria: 1. patients who have had other malignant tumors within the previous 5 years (except cured carcinoma in situ and basal cell carcinoma of the skin); 2. prior irinotecan/irinotecan liposome-based chemotherapy; 3. large pleural effusions or ascites requiring intervention; 4. active, uncontrolled bacterial, viral or fungal infections requiring systemic therapy 5. known active HIV infection; untreated active HBV and HCV infection 6. a combination of uncontrolled systemic diseases, including cardiovascular diseases such as unstable angina pectoris, myocardial infarction, congestive heart failure, severe unstable ventricular arrhythmia, and a history of severe pericardial disease; uncontrollable hypertension (defined as systolic blood pressure ≥140 mmHg and/or diastolic blood pressure ≥90 mmHg after regulated antihypertensive medication) or a history of critical hypertension, hypertensive encephalopathy; uncontrollable diabetes; and controlled diabetes mellitus, etc; 7. the presence of severe gastrointestinal-like illness (including active bleeding, greater than grade 1 obstruction, greater than grade 1 diarrhea, or gastrointestinal perforation) 8. history of cesarean section, open thoracic surgery or bowel resection within 28 days prior to enrollment; 9. presence of interstitial pneumonia or pulmonary fibrosis; 10. known hypersensitivity or intolerance to therapeutic drugs or their excipients; 11. history of pulmonary hemorrhage/coughing up ≥ grade 2 (defined as at least 2.5 mL of bright red blood) within 1 month prior to enrollment; 12. presence of arterial embolism, severe hemorrhage (other than hemorrhage due to surgery), or a predisposition to existing embolism or severe hemorrhage within 6 months prior to enrollment 13. presence of central nervous system metastases; 14. the presence of serum albumin ≤ 3 g/dL 15. those using strong inhibitors or inducers of CYP3A4, CYP2C8 and UGT1A1; 16. women who are pregnant or breastfeeding, and patients of childbearing potential who refuse to use adequate contraception during the course of this trial (from study enrollment to the end of primary study focus or surgical treatment); 17. who have participated in another study within 30 days prior to the administration of the first dose of study drug 18. patients who, in the judgment of the investigator, are not suitable for participation in this study.