Participants receive Sintilizumab 200 mg, intravenously (IV) every 3 weeks(Q3W);plus Apatinib 250 mg twice daily (BID) by continous oral adminstration for 14 days, followed by a recovery period of 7 days; plus Tegafur gimeracil oteracil potassium capsules (40mg for body surface area < 1.25/m^2, 50mg/m^2 for body surface area 1.25-1.5m^2, 60mg for body surface area > 1.5/m^2) BID by continous oral adminstration for 14 days, followed by a recovery period of 7 days, plus Oxaliplatin 85 mg/m^2, IV Q3W; for 4-6 cycles followed by Cindilizumab plus Tegafur gimeracil oteracil potassium capsules.
To evaluate the efficacy and safety of Sintilimab combined with apatinib and chemotherapy as First-line or second-line Therapy in Treatment of HER-2 negative MSS Advanced or Metastatic GC or GEJ Cancer. At the same time, the correlation between tissue programmed death ligand-1(PD-L1) expression and blood circulating tumor cell(CTC) counts and the efficacy of immune combination therapy was also explored.