Adjuvant chemoradiation in pancreatic cancer: impact of radiotherapy dose on survival

BackgroundTo evaluate the impact of radiation dose on overall survival (OS) in patients treated with adjuvant chemoradiation (CRT) for pancreatic ductal adenocarcinoma (PDAC).MethodsA multicenter retrospective analysis on 514 patients with PDAC (T1-4; N0-1; M0) treated with surgical resection with macroscopically negative margins (R0-1) followed by adjuvant CRT was performed. Patients were stratified into 4 groups based on radiotherapy doses (group 1: <45Gy, group 2: 45 and<50Gy, group 3: 50 and<55Gy, group 4: 55Gy). Adjuvant chemotherapy was prescribed to 141 patients. Survival functions were plotted using the Kaplan-Meier method and compared through the log-rank test.ResultsMedian follow-up was 35months (range: 3-120months). At univariate analysis, a worse OS was recorded in patients with higher preoperative Ca 19.9 levels (90U/ml; p<0.001), higher tumor grade (G3-4, p=0.004), R1 resection (p=0.004), higher pT stage (pT3-4, p=0.002) and positive nodes (p<0.001). Furthermore, patients receiving increasing doses of CRT showed a significantly improved OS. In groups 1, 2, 3, and 4, median OS was 13.0months, 21.0months, 22.0months, and 28.0months, respectively (p=0.004). The significant impact of higher dose was confirmed by multivariate analysis.ConclusionsIncreasing doses of CRT seems to favorably impact on OS in adjuvant setting. The conflicting results of randomized trials on adjuvant CRT in PDAC could be due to <45Gy dose generally used.