Association Between Immune‐Related Adverse Events and Treatment Outcomes in Advanced Gastric Cancer Patients Receiving Nivolumab Plus Chemotherapy: A Retrospective Study

ABSTRACT Background Immune‐related adverse events (irAEs) have been linked to improved outcomes in patients undergoing treatment with immune checkpoint inhibitors (ICIs) for various cancers. However, the relationship between irAEs and overall survival (OS) in patients with advanced gastric cancer (AGC) receiving chemoimmunotherapy remains unclear. This study aimed to explore the association between irAEs and treatment outcomes in patients with AGC receiving chemotherapy plus nivolumab. Methods This retrospective study analyzed clinical data from patients with HER2‐negative AGC who received first‐line chemotherapy (SOX, CapeOX, or FOLFOX) plus nivolumab at the National Cancer Center Hospital between November 2021 and February 2023. Patients were stratified into two groups based on the occurrence of irAEs. Outcomes, including OS and progression‐free survival (PFS), were compared using Kaplan–Meier analysis, landmark analysis, and Cox proportional hazards regression. Results Among the 60 patients analyzed, 15 (25%) developed irAEs of any grade, with 3 patients (5%) experiencing grade ≥ 3 irAEs. Patients with irAEs had significantly longer OS and PFS in comparison to those without irAEs (median OS: not reached vs. 17.1 months, p < 0.01; median PFS: not reached vs. 6.8 months, p < 0.01). Multivariate analysis identified the occurrence of irAEs as a favorable prognostic factor for OS (hazard ratio: 0.13; 95% CI: 0.03–0.59; p < 0.01). Conclusion This study suggests that the occurrence of irAEs is associated with improved survival outcomes in patients with AGC receiving chemotherapy plus nivolumab. IrAEs may serve as a predictive marker for treatment response in this setting.