Single fraction of HDR brachytherapy for prostate cancer: Results of the SiFEPI phase II prospective trial

To report the results of the Single Fraction Early Prostate Irradiation (SiFEPI) phase 2 prospective trial. The SiFEPI trial (NCT02104362) evaluated a single fraction of high-dose rate brachytherapy (HDB) for low- (LR) and favorable-intermediate (FIR) risk prostate cancers. After rectal spacer placement, a single fraction of 20 Gy was delivered to the prostate. Oncological outcome (biochemical (bRFS) and local (lRFS) relapses, disease-free (DFS) and overall (OS) survivals and toxicity (acute/late genito-urinary (GU), gastro-intestinal (GI) and sexual (S) toxicities were investigated. From 03/2014 to 10/2017, 35 pts were enrolled, of whom 33 were evaluable. With a median age of 66 y [46–79], 25 (76 %) and 8 (24 %) pts were LR and FIR respectively. With a MFU of 72.8 months [64–86], 6y-bRFS, lRFS and mRFS were 62 % [45–85], 61 % [44–85] and 93 % [85–100] respectively while 6y-DFS, CSS and OS were 54 % [37–77], 100 % and 89 % [77–100] respectively. Late GU, GI and S toxicities were observed in 11 pts (33 %;18G1), 4 pts (12 %;4G1) and 7 pts (21 %;1G1,5G2,1G3) respectively. Biochemical relapse (BR) was observed in 11 pts (33 %;7LR,4FIR) with a median time interval between HDB and BR of 51 months [24–69]. Nine of these pts (82 %) presented a histologically proven isolated local recurrence. Long-term results of the SiFEPI trial show that a single fraction of 20 Gy leads to sub-optimal biochemical control for LR/FIR prostate cancers. The late GU and GI toxicity profile is encouraging, leading to consideration of HDB as a safe irradiation technique.