Neoadjuvant S-1 With Concurrent Radiotherapy Followed by Surgery for Borderline Resectable Pancreatic Cancer: A Phase II Open-Label Multicenter Prospective Trial (JASPAC05).

Objective This study assessed whether neoadjuvant chemoradiotherapy (CRT) with S-1 increases the R0 resection rate in borderline resectable pancreatic cancer (BRPC). Summary background data Although a multidisciplinary approach that includes neoadjuvant treatment has been shown to be a better strategy for BRPC than upfront resection, a standard treatment for BRPC has not been established. Methods A multicenter, single-arm, phase II study was performed. Patients who fulfilled the criteria for BRPC received S-1 (40 mg/m bid) and concurrent radiotherapy (50.4 Gy in 28 fractions) before surgery. The primary endpoint was the R0 resection rate. At least 40 patients were required, with a one-sided α = 0.05 and β = 0.05 and expected and threshold values for the primary endpoint of 30% and 10%, respectively. Results Fifty-two patients were eligible, and 41 were confirmed to have definitive BRPC by a central review. CRT was completed in 50 (96%) patients and was well tolerated. The rate of grade 3/4 toxicity with CRT was 43%. The R0 resection rate was 52% among the 52 eligible patients and 63% among the 41 patients who were centrally confirmed to have BRPC. Postoperative grade III/IV adverse events according to the Clavien-Dindo classification were observed in 7.5%. Among the 41 centrally confirmed BRPC patients, the 2-year overall survival rate and median overall survival duration were 58% and 30.8 months, respectively. Conclusions S-1 and concurrent radiotherapy appear to be feasible and effective at increasing the R0 resection rate and improving survival in patients with BRPC. Trial registration UMIN000009172.