Unresectable/Metastatic Gastric Cancer

The combination of immune checkpoint inhibitors and platinum containing dual drugs are more used as a first-line therapeutic approach for patients diagnosed with advanced gastric cancer for its superior efficacy. However, there are no standard recommendations for subsequent treatment after progression on first-line therapy. Here, the investigators conduct this open-label, monocenter, single arm phase II study to evaluate whether sintilimab in combination with irinotecan, leucovorin folinate and fluorouracil can be the second-line therapy for patients diagnosed with HER2-negative unresectable or metastatic gastric cancer progression on first-line therapy. Patients participated in this study will receive sintilimab 3mg/kg for patients with body weight\<60kg or 200mg for patients with body weight ≥ 60kg, plus irinotecan 180mg/m2 intravenous infusion, leucovorin folinate 400mg/m2 intravenous infusion and fluorouracil 400mg/m2 intravenous injection followed by 2400mg/m2 intravenous infusion for 48 hours, repeated every two weeks. The primary endpoint is 5-month progression-free survival (PFS) rate. The investigators estimated that 27 patients were necessary. Secondary endpoints include overall survival, progression-free survival, objective response rate, disease control rate and safety for unresectable or metastatic gastric cancer. Exploratory endpoint is to detect the baseline ctDNA level of patients before initial treatment.