Impact of Immune Checkpoint Inhibitors on Survival Outcomes in Advanced Gastric Cancer in Japan: A Real‐world Analysis

Background: Nivolumab was approved for the treatment of advanced gastric cancer in 2017 in Japan. The aim of this study was to assess the impact of nivolumab in a real-world clinical setting. Methods: This single-institutional retrospective study included patients with advanced gastric or esophagogastric junction adenocarcinoma and a history of first-line chemotherapy with platinum-based doublet or triplet regimens between 2010 and 2020. To assess the impact of nivolumab on survival, the patients were divided based on the year of nivolumab approval into a pre-2017 (2010-2016) group and a post-2017 (2017-2020) group. Results: From a total of 1918 patients, 1093 were excluded. There were 533 patients in the pre-2017 group and 292 in the post-2017 group. Immune checkpoint inhibitors were used significantly more often in the post-2017 group than in the pre-2017 group (8.6% vs. 47.9%). Median overall survival was significantly longer in the post-2017 group (16.9 vs. 13.9 months; hazard ratio [HR] 0.75, 95% confidence interval [CI] 0.63-0.90; p < 0.01). The proportion of patients transitioning to third-line treatment was higher in the post-2017 group than in the pre-2017 group (56.3% vs. 43.8%, p < 0.01). Median survival outcomes following progression on second-line treatment were significantly longer in the post-2017 group (4.3 vs. 3.2 months; HR 0.70, 95% CI 0.57-0.86; p < 0.01). Conclusion: The proportion of patients transitioning to third-line treatment and survival outcomes following progression on second-line treatment have improved since the approval of nivolumab. This drug might help to prolong overall survival in real-world practice.