Neoadjuvant of Sintilimab Combined Weekly Metronomic Chemotherapy (PLOF) for Resectable Locally Advanced Gastric Cancer

Inclusion Criteria: Signed written Informed Consent Form Male or female, age ≥ 18 years old Histologically confirmed gastric adenocarcinoma, diagnosed as locally progressive according to the AJCC 8th ed, cTNM diagnosis of cT3-4aN1-3M0 and resectable lesion as assessed by the investigator No prior systemic therapy such as surgery, radiotherapy, or immunotherapy for the disease at hand Consent to radical surgical treatment and no contraindications to surgery as determined by the surgeon ECOG PS: 0-1 score Expected survival > 6 months Adequate organ function, must meet the following laboratory specifications: 8.1 Absolute neutrophil count (ANC) ≥ 1.0x10^9/L; 8.2 Platelets ≥ 80x10^9/L; 8.3 Hemoglobin > 7g/dL; 8.4 Total bilirubin ≤ 1.5 x upper limit of normal (ULN) (Total bilirubin > 1.5 x ULN but direct bilirubin ≤ ULN are allowed to be enrolled); 8.5 AST, ALT ≤ 2.5×ULN; 8.6 Blood creatinine ≤ 1.5 x ULN or creatinine clearance ≥ 60 ml/min; 8.7 INR or PT ≤ 1.5 times ULN; 8.8 TSH within normal range (Enrollment allowed if baseline TSH is outside normal range but FT4 is within normal range); 8.9 Myocardial enzyme profile within normal range; Negative pregnancy test in women of childbearing age Need to use contraception with an annual failure rate of less than 1% if there is a risk of conception Exclusion Criteria: Endoscopically show signs of active bleeding from the lesion Current participation in an interventional clinical study or treatment with another investigational drug or use of an investigational device within 4 weeks prior to the first dose of study drug Prior therapy with anti-PD-1, anti-PD-L1, or anti-PD-L2 agents, or agents targeting CTLA-4, OX-40, CD137, etc. Diagnosis of a malignant disease other than gastric cancer within 5 years prior to the first dose of therapy Active autoimmune disease requiring systemic therapy within 2 years prior to the first dose of the drug Live vaccination within 30 days prior to the first administration of the drug Have received systemic systemic therapy with proprietary Chinese medicines with antitumor indications or immunomodulatory drugs within 2 weeks prior to the first administration of the drug Have received systemic glucocorticoid therapy or any other form of immunosuppressive therapy within 7 days prior to the first dose of treatment Has not fully recovered from any intervention-induced toxicity and/or complications (excluding malaise or alopecia) prior to initiation of therapy Known allogeneic organ transplantation (except corneal transplantation) or allogeneic hematopoietic stem cell transplantation Known hypersensitivity to drugs used in this study Known history of HIV infection Untreated active hepatitis B Active HCV infection Pregnant or lactating women The presence of any serious or uncontrolled systemic disease Other factors that, in the judgment of the investigator, may affect the outcome of the study