Association of Adjuvant Immunotherapy With Survival Outcomes Among Patients With Locally Advanced Gastric Cancer After Neoadjuvant Immunochemotherapy: A Propensity Score-Matched Cohort Study

Background For patients with locally advanced gastric cancer (LAGC) who have received neoadjuvant immunochemotherapy (NAIC), it has been recognized that adjuvant chemotherapy after operation is indispensable for the majority of cases; nevertheless, whether additional postoperative adjuvant immunotherapy is needed is still an unanswered question.Methods A total of 233 LAGC patients who received NAIC were included in this study, of which 115 patients received adjuvant immunochemotherapy (AIC) and 118 patients received adjuvant chemotherapy (AC) only. After propensity score matching (PSM) for 1:1 matching, 94 patients were included in both the AC and AIC groups. Immune-related adverse events (irAEs), 3-year disease-free survival (DFS) and overall survival (OS) outcomes were compared between the two groups of patients.Results After PSM, 188 patients were included in the study. AIC group did not demonstrate a significant advantage in terms of 3-year DFS (AC: 77.6% vs. AIC: 75.5%, P=0.534) and 3-year OS (AC: 88.2% vs. AIC: 86.1%, P=0.593) compared to the AC group. However, the total number of irAEs in the AIC group was significantly higher than that in the AC group (AC: 27.66% vs. AIC: 43.62%, P = 0.021).Conclusion For LAGC patients after NAIC, postoperative adjuvant immunotherapy may not be warranted for most patients across all ypTNM stages, pending validation from prospective randomized controlled trials.