To investigate the efficacy and safety of sintilimab injection combined with S-1 capsules/oxaliplatin injection (SOX) regimen as neoadjuvant therapy for patients with locally advanced gastric cancer (LAGC).

LAGC patients were divided into control group and treatment group based on treatment methods. The control group received neoadjuvant chemotherapy with the SOX regimen, with intravenous infusion of oxaliplatin injection 135 mg·m^-2 on the first day of each cycle, and S-1 capsules were administered orally according to the patient’s body surface area (40 mg each time for <1.25 m², 50 mg each time for 1.25-1.50 m², and 60 mg each time for >1.50 m²), twice a day, for 1-14 days, with every 3 weeks as one cycle. The treatment group received sintilimab injection 200 mg intravenously on the first day of each cycle (every 3 weeks as one cycle) in addition to the control group’s treatment. After both groups completed 4 cycles of treatment, radical gastrectomy+D₂ lymph node dissection was performed. The clinical efficacy, tumor marker levels, safety, and survival status of the two groups were compared.

The control group included 48 cases, and the treatment group included 52 cases. The effective rates of the control group and the treatment group were 52.08% (25 cases/48 cases) and 73.08% (38 cases/52 cases), respectively, After treatment, the levels of carcinoembryonic antigen (CEA) in the control group and the treatment group were (21.08±3.30) and (19.52±2.90) ng·mL^-1, respectively; the levels of carbohydrate antigen (CA) 19-9 were (43.89±5.11) and (41.57±4.73) U·mL^-1, respectively; the levels of CA 72-4 were (24.82±3.15) and (23.18±2.79) U·mL^-1, respectively; the median progression-free survival was 27 and 40 months, respectively; and the median overall survival was 33 and 46 months, respectively. The above indicators of the treatment group were all statistically significantly different from those of the control group (P<0.05, P<0.01). The incidence rates of nausea and vomiting in the control group and the treatment group were 25.00% (12 cases/48 cases) and 15.38% (8 cases/52 cases), respectively; the incidence rates of diarrhea were 14.58% (7 cases/48 cases) and 11.54% (6 cases/52 cases), respectively; the incidence rates of bone marrow suppression were 29.17% (14 cases/48 cases) and 32.69% (17cases/52 caes), respectively, with no statistically significant difference (all P>0.05).

Sintilimab combined with SOX regimen as neoadjuvant therapy for LAGC patients can achieve good clinical efficacy, improve functional status, prolong survival, reduce tumor marker levels, and has fewer surgery-related complications and good safety.