Effect of chemoimmunotherapy on survival in stage II-IV gastric adenocarcinoma: An NCDB retrospective study.

Abstract

415 Background: Gastric adenocarcinoma remains a leading cause of cancer-related deaths worldwide. Surgery with curative intent, combined with perioperative chemotherapy, is the standard treatment; however, recurrence rates remain high, highlighting the need for additional strategies. Recent clinical trials suggest survival benefits with the addition of immunotherapy in both metastatic and resectable disease. Whether these findings translate to broader, real-world populations is unclear. We conducted a retrospective cohort study using the National Cancer Database to examine immunotherapy utilization over time and the impact of combined chemoimmunotherapy on survival in gastric adenocarcinoma. Methods: We identified patients with stage II–IV gastric adenocarcinoma treated between 2004 and 2022 who received chemotherapy, immunotherapy, and/or surgery. Immunotherapy use over time was analyzed separately for stage II/III and stage IV disease. Treatment groups were defined as follows: stage II/III—surgery plus chemotherapy vs. surgery plus chemoimmunotherapy; stage IV—chemotherapy alone vs. chemoimmunotherapy. Demographic, clinical, and pathologic variables were compared using chi-square and t tests. Survival was analyzed using Kaplan–Meier methods. Results: From 2004 to 2022, 66,117 patients with gastric adenocarcinoma (stage II/III: 45.2% (n=29,889), stage IV: 54.8% (n=36,228) were identified. Among stage II/III patients, treatment included surgery plus chemotherapy (28,475; 95.4%), and surgery plus chemoimmunotherapy (1,414; 4.7%). Among stage IV patients, treatment included chemotherapy (29,646; 81.8%) chemoimmunotherapy (6,582; 18.2%). Immunotherapy use increased substantially, from less than 1% of patients in 2012 to 19.2% of stage II/III and 39.9% of stage IV patients in 2022. For stage II/III patients, there were no significant differences in median positive lymph nodes or margin status across treatment groups. Survival analysis demonstrated significant improvements with chemoimmunotherapy. Median survival for stage II/III: surgery plus chemotherapy, 42.8 months (95% CI: 41.6–43.9); surgery plus chemoimmunotherapy, 55.6 months (95% CI: 45.4–78.8); p < 0.001. Median survival for stage IV: chemotherapy, 9.23 months (95% CI: 9.10–9.33), 13.83 months (95% CI: 13.44–14.29); p < 0.001. Conclusions: Stage II–IV gastric adenocarcinoma patients treated with chemoimmunotherapy experience significantly longer survival compared with chemotherapy alone. Further studies are warranted to refine patient selection and optimize treatment intensity and duration for maximum therapeutic benefit.