Improved survival with adjuvant external-beam radiation therapy in lymph node-negative pancreatic cancer: a United States population-based assessment

BACKGROUND: Although chemoradiation often is administered as an adjuvant to pancreatic cancer surgery, recent reports have disputed the benefit of radiation therapy. The objective of this study was to determine the effect of adjuvant radiation therapy in patients with locally confined, lymph node-negative (N0) pancreatic cancer. METHODS: The Surveillance, Epidemiology, and End Results registry was used to identify patients who had undergone cancer-directed surgery for N0 pancreatic adenocarcinoma between 1988 and 2003. Kaplan-Meier survival curves were constructed to compare overall survival between patients who did and did not receive adjuvant external-beam radiation therapy (EBRT). Multivariate Cox regression analysis was used to determine the prognostic significance of EBRT when additional clinicopathologic factors were assessed. The analysis also examined the potential treatment selection bias of patients with survival <3 months. RESULTS: A cohort of 1930 surgical patients with N0 disease was identified. The median survival was 17 months. Irradiated patients had significantly better survival compared with nonirradiated patients (20 months vs 15 months, respectively; P < .001). On multivariate analysis, adjuvant EBRT (hazard ratio [HR], 0.72; 95% confidence interval [95% CI], 0.63-0.82; P < .001), age, grade, tumor classification, and tumor location were independent predictors of survival. When patients with survival <3 months were excluded from the analysis, no difference in survival between the EBRT group and the nonradiation group was noted on univariate comparison (P value not significant). However, on multivariate analysis, EBRT remained an independent predictor of improved overall survival (HR, 0.87; 95% CI, 0.75-1.00; P = .044). CONCLUSIONS: Adjuvant EBRT was associated with improved survival in patients with operable, N0 pancreatic cancer. Its use should be considered in patients who have early-stage N0 disease.