To compare the prognosis and postoperative complications of patients with locally advanced gastric cancer who received conversion therapy based on combination immunotherapy (IBCT) with those who received direct surgery, and establish a prediction model for common postoperative complications.

A total of 897 patients with gastric cancer who received surgical treatment from January 2019 to May 2022 were selected, and the baseline data, postoperative complications and postoperative pathology of 169 patients treated with IBCT and 338 patients treated with direct surgical treatment were retrospectively analyzed with 1:2 propensity score matching analysis. SPSS 26, GraphPad Prism 8 and R.4.2.1 were used for data analysis. Univariate and multivariate Logistic regression analysis was applied and ROC curve was drawn. The pre-model of the most common postoperative complications was established by drawing a column graph, and the multivariate analysis results were visualized. P < 0.05 was considered to be statistically significant.

Patients treated with IBCT had a better prognosis than those treated with direct surgery, but had a higher rate of postoperative complications. Postoperative infection is the most common postoperative complication. Multivariate Logistic regression analysis showed that age (OR 1.08, 95% CI 1.01-1.14, P=0.015) and body mass index (OR 1.14, 95% CI 0.99-1.31, P=0.026) were independent risk factors for postoperative respiratory system associated infection. Intraoperative blood loss (OR 1.01, 95% CI 1.01-1.01, P=0.009) and operative time (OR 1.01, 95% CI 1.01-1.02, P=0.007) were independent risk factors for abdominal infection.

Conversion therapy combined with immunotherapy can improve the prognosis of patients. Elderly patients with high BMI should strengthen perioperative management and pay attention to fine operation in order to reduce the incidence of perioperative infection.