Association of adjuvant radiotherapy with survival after margin-negative resection of pancreatic ductal adenocarcinoma: a propensity-matched national cancer database (ncdb) analysis

Abstract

INTRODUCTION There is conflicting evidence for the benefit of adjuvant radiotherapy (RT) after resection of pancreatic ductal adenocarcinoma (PDAC), especially for margin-negative (R0) resections. We aimed to evaluate the association of adjuvant RT with survival after R0 resection of PDAC. METHODS Using National Cancer Database (NCDB) data from 2004 to 2013, we identified patients with R0 resection of nonmetastatic PDAC. Patients with neoadjuvant radiotherapy and chemotherapy and survival <6 months were excluded. Propensity score matching was used to account for treatment selection bias. A multivariable Cox proportional hazards model was then used to analyze the association of RT with survival. RESULTS Of 4547 (36%) RT and 7925 (64%) non-RT patients, 3860 RT and 3860 non-RT patients remained in the cohort after matching. Clinicopathologic and demographic variables were well balanced after matching. Lymph node metastases were present in 68% (44% N1, 24% N2). After matching, RT was associated with higher survival (median 25.8 vs 23.9 mo, 5-yr 27% vs 24%, P < 0.001). After multivariable adjustment, RT remained associated with a survival benefit (HR 0.89, 95% CI 0.84-0.94, P < 0.001). Stratified and multivariable interaction analyses showed that this benefit was restricted to patients with node-positive disease: N1 (HR: 0.68, CI95%: 0.62-0.76, P = 0.007) and N2 (HR: 0.59, CI95%: 0.54-0.64, P = 0.04). CONCLUSIONS In this large retrospective cohort study, adjuvant RT after R0 PDAC resection was associated with a survival benefit in patients with node-positive disease. Adjuvant RT should be considered after R0 resection of PDAC with node-positive disease.