Conversion Therapy of Sintilimab in Combination With Apatinib and Chemotherapy in Stage IV Gastric Cancer

Inclusion Criteria:

* gastric adenocarcinoma confirmed by gastroscopy and pathology (histologically/cytologically ) ;
* life expectancy of ≥3-month；
* unresectable patients who were initially diagnosed as stage IV (clinical stage, American Joint Committee on Cancer 8th edition);
* Eastern Cooperative Oncology Group performance status: 0-1;
* must have at least 1 of the following unresectable factors indicated by CT, MRI or positron emission tomography(PET)-CT:

  1. N3 lymphatic metastasis;
  2. Extensive or bulky lymph nodes;
  3. T4b;
  4. Hepatic metastasis: ≤5 lesions, total diameter of ≤8cm;
  5. Peritoneal metastasis (CY1, P1);
  6. Kukernburg tumor;
* adequate organ function;
* pregnant test negative of females of childbearing potential , and willing to use adequate contraception;
* written Informed Consensus Form;

Exclusion Criteria:

* prior use of any checkpoint inhibitor treatment, including PD-1, programmed cell death ligand-1(PDL-1), CTLA4 etc;
* Her-2 positive with willing to use herceptin treatment;
* prior active autoimmune disease or history of autoimmune disease;
* clinically significant cardiovascular and cerebrovascular diseases, including but not limited to severe acute myocardial infarction within 6 months before enrollment, unstable or severe angina, or coronary artery bypass surgery, Congestive heart failure (New York heart association (NYHA) class \> 2), ventricular arrhythmia which need medical intervention, left ventricular ejection fraction(LVEF) \< 50%;
* not controlled hypertension;
* prior systemic treatment to metastatic disease；
* previous digestive tract bleeding history within 3 months or evident gastrointestinal bleeding tendency;
* history of immunodeficiency including seropositivity for human immunodeficiency virus (HIV), or other acquired or congenital immune-deficient disease, or active hepatitis ;
* patients who may receive vaccination during study period;
* mental disorders history, or psychotropic drug abuse history;
* unable to orally administration;