[Short-term effects and safety outcomes of the combination of tislelizumab and neoadjuvant chemotherapy in the perioperative treatment of locally advanced gastric cancer].

<b>Objective:</b> In this study, we aimed to investigate the short-term efficacy and safety of perioperative administration of the PD-1 inhibitor tislelizumab combined with the SOX regimen (oxaliplatin plus S-1) in patients with locally advanced gastric cancer, and to identify factors influencing therapeutic outcomes. <b>Methods:</b> In this retrospective cohort study, we analyzed clinical data of 166 patients who had undergone perioperative therapy and D2 radical gastrectomy in the Department of General Surgery, First Medical Center of Chinese PLA General Hospital between September 2021 and September 2023. The cohort comprised 140 men and 26 women, of median age 62 years (range: 30-75). The patients were allocated to two groups: 62 receiving tislelizumab plus SOX (combination therapy group), and 104 SOX alone (chemotherapy-only group). Primary outcomes included pathological complete response rate, treatment-related adverse events, and complications of surgery. Secondary outcomes comprised major pathological response rate, tumor regression grade (Grades 1-2 denoting favorable response, Grade 3 moderate, and Grades 4-5 poor response), R0 resection rate, and short-term survival outcomes (1-year disease-free and overall survivals). Risk factors associated with pCR in the combination group were also analyzed. <b>Results:</b> The combination therapy group exhibited significantly higher rates of pCR (25.8% vs. 8.7%, χ²=8.93, <i>P</i>=0.003) and Grade 1 tumor regression (25.8% vs. 16.3%, χ²=15.32, <i>P</i>=0.001) than the chemotherapy-only group. There were no statistically significant differences in major pathological response rates (41.9% vs. 39.4%), R0 resection rates (96.8% vs. 97.1%,), treatment- related adverse events (48.4% vs. 42.3%,), surgical complications (9.7% vs. 12.5%), 1-year disease-free survival (82.3% vs. 78.8%), or 1-year overall survival (93.5% vs. 91.3%), There were no statistically significant differences (all <i>P</i>>0.05). Multivariate logistic analysis identified neural invasion as an independent risk factor for reduced pCR in the combination group (OR=0.10, 95%CI:0.01-0.85,<i>P</i>=0.035). <b>Conclusions:</b> Perioperative tislelizumab combined with SOX chemotherapy improves pathological response rates in patients with locally advanced gastric cancer and has favorable short-term efficacy and safety profiles. Neural invasion may diminish the therapeutic efficacy of immunotherapy.