Survival benefit of adjuvant chemoradiotherapy for positive or close resection margin after curative resection of pancreatic adenocarcinoma

Background This study was conducted to identify patients who may benefit from adjuvant chemoradiotherapy (CRT) for positive or close resection margin (RM) after curative resection of pancreatic adenocarcinoma. Methods From 2004 to 2015, total of 472 patients with pancreatic adenocarcinoma underwent curative resection. After excluding patients with RM > 2 mm or unknown, remaining 217 patients were retrospectively analyzed. Forty-six (21.2%) patients were treated with adjuvant chemotherapy alone (CTx; mainly gemcitabine-based), 142 (65.4%) with adjuvant CRT (mainly upfront), and 29 (13.4%) patients didn’t receive any adjuvant therapy (noTx group). Results Locoregional recurrence rate was significantly lower in the CRT group (43.7%) than in the CTx group (71.7%) or noTx group (65.5%) (p = 0.001). Significant survival benefits of CRT over CTx (HR 0.602, p = 0.020 for overall survival (OS); HR 0.599, p = 0.016 for time to any recurrence (TTR)) were demonstrated in multivariate analysis. CRT group had more 5-year survivors than other groups. In the subgroup analysis, such benefits of adjuvant CRT over CTx was observed only in patients with head tumor & vascular RM > 0.5 mm, but not in patients with body/tail tumor or vascular RM ≤ 0.5 mm. In the CRT group, radiation dose≥54 Gy was significantly associated with better TTR and OS. Conclusions Adjuvant CRT could improve TTR and OS compared to adjuvant CTx alone in patients with close RM under 2 mm. Radiation dose escalation may be beneficial when feasible. Modern CRT regimen–based randomized evidence is needed for these high-risk patients.