Sintilimab combined with chemotherapy in conversion therapy of advanced gastric cancer: A retrospective study.

e16012 Background: Gastric cancer is the fifth most common cancer in the world and the third leading cause of cancer death. At present, traditional chemotherapy is still the main treatment method of advanced gastric cancer, but the efficacy is limited. Immunotherapy has been identified as a treatment for chemotherapy-refractory gastric cancer, and sintilimab is a fully human IgG4 monoclonal antibody that binds to programmed cell death receptor-1 (PD-1). This study aims to investigate the efficacy of sintilimab combined with chemotherapy in patients with inoperable metastatic gastric cancer and analyze the prognostic factors of these patients. Methods: Patients with advanced gastric cancer which were initially treated unresectable and with distant metastasis in Zhejiang Cancer Hospital from August 2018 to December 2021 were retrospectively analyzed in this research. Patients received sintilimab combined with chemotherapy (PS regimen) ：sintilimab 200mg, day 1, paclitaxel was administered intravenously (150 mg/m 2 ) on day 1, and S-1 was administered orally (80 mg/m 2 /day) on days 1–14 of a 3-week cycle. The primary endpoints were treatment efficiency; and the secondary endpoint was safety and overall survival (OS) time. Results: A total of 66 patients were enrolled, including 43 males and 23 females, with an average age of 62.2 years (29-77 years). All of these patients had one or more distant metastases (liver 28 cases, peritoneum 20 cases, retroperitoneal lymph node 21 cases and ovary 5 cases). 33 patients (50%) underwent surgery, including conversion surgery (26 cases), palliative surgery (7 cases). The mean OS of patients with conversion surgery was 19.2 months (95%CI 16.5̃21.9 months), and the 2-year survival rate was 50.0%. The mean OS of non-conversion surgery was 16.9 months (95%CI 12.9̃20.1 months), and the 2-year survival rate was 29.1% (P=0.028). 24 (92.3%) cases had R0 resection. Multivariate analysis showed that postoperative CA125 level was an independent risk factor for prognosis of these gastric cancer patients. Conclusions: Sintilimab combined with chemotherapy is safe and effective, and combined with conversion surgery can improve the prognosis of patients with partially unresectable advanced gastric cancer.