Background: Adjuvant chemoradiotherapy improved survival in patients with resected gastric adenocarcinoma in the Southwest Oncology Group/Intergroup 0116 trial. Our objective was to examine the impact of adjuvant treatment on overall survival (OS) in the general population.
Methods: Patients 18-85 years old who had undergone resection of non-metastatic gastric adenocarcinoma between May 2000 and December 2003, were identified from the Surveillance Epidemiology and End Results (SEER) database. Patients who had received pre-operative irradiation, had unknown stage or radiation status, or had a survival of 3 months or less from the date of diagnosis were excluded. Survival of those who received post-operative irradiation was compared with those who did not; Kaplan-Meier methods and Cox proportional hazards models were used.
Results: Of 4,041 patients, there was improved survival for those receiving adjuvant irradiation for stages III and IVM0, with a median OS of 31 versus 24 months (P = 0.005) and 20 versus 15 months (P < 0.001), respectively, and a trend for improved survival in univariate analysis of stage II (P = 0.0535). In final adjusted analysis, adjuvant irradiation significantly improved OS in stages III (HR: 0.71, P = 0.0007) and IVM0 (HR: 0.66, P < 0.0001). Adjusted analysis using a propensity score suggested that the benefit of adjuvant irradiation was similar in stage-II and -III patients. However, there was no statistical improvement in survival for stage-Ib and -II patients who had received adjuvant irradiation.
Conclusions: In this population-based analysis, adjuvant radiotherapy for stage-III and IVM0 gastric cancer significantly improved OS. Analysis of stage-Ib and -II patients is limited by small numbers, but there may not be the same benefit.