Does adjuvant radiation provide any survival benefit after an R1 resections for pancreatic cancer?

Background: The benefit of adding external beam radiation to adjuvant chemotherapy in patients that have undergone a margin positive resection for early stage, pancreatic ductal adenocarcinoma has not been determined definitively.
Methods: The National Cancer Data Base was queried to evaluate the utility of adjuvant radiation in patients with pathologic stage I-II pancreatic ductal adenocarcinoma who underwent upfront pancreatoduodenectomy with a positive margin (margin positive resection) between 2004 and 2013.
Results: In the study, 1,392 patients met inclusion criteria, of whom 263 (18.9%) were lymph node-negative (pathologic stages IA, IB, IIA) and 1,129 (81.1%) were node-positive (pathologic stage IIB); 938 (67.4%) patients received adjuvant radiation and chemotherapy, while 454 (32.6%) received adjuvant chemotherapy alone. Cox modeling stratified by nodal status demonstrated the benefit of radiation to be statistically significant only in node positive patients (hazard ratio 0.81, 95% confidence interval, 0.71-0.93). Node-positive patients receiving adjuvant radiation and chemotherapy had an adjusted median survival of 17.5 months vs 15.2 months for those receiving adjuvant chemotherapy alone (P=.003). In patients who had negative nodes, there was no difference in overall survival with radiation (22.5 vs 23.6 months, P=.511).
Conclusion: Addition of radiation to adjuvant chemotherapy after a margin positive resection confers a survival benefit albeit limited (about 2 months) in patients with node-positive pancreatic head cancer. (Surgery 2017;160:XXX-XXX.).
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