Ultra-hypofractionated radiotherapy combined with HDR brachytherapy: An optimized treatment.

[PURPOSE] To evaluate safety and efficacy of ultra hypofractionated radiotherapy (UHF) combined with high dose rate brachytherapy boost (HDR-BB) in comparison to a moderately hypo-fractionated (MHF) regimen, in patients treated for intermediate risk prostate cancer.

[MATERIALS/METHODS] 199 patients with intermediate risk prostate cancer were recruited in the experimental UHF treatment cohort of 25 Gy in 5 fractions plus a 15 Gy HDR-BB. They were compared to two historical control groups, treated with either 36 Gy in 12 fractions (152 patients) or 37.5 Gy in 15 fractions (311 patients) with an identical HDR-BB. The study reported the biochemical cure rate (BCR) defined as PSA < 0.2 ng/ml at 4 years, as well as biochemical relapse-free survival (BRFS) and overall survival (OS). Additionally, genitourinary (GU), gastrointestinal (GI), and sexual toxicities were evaluated.

[RESULTS] At the time of analysis, median follow up was respectively 36, 90 and 102 months for the UHF, 36 Gy and 37.5 Gy group. The BCR was 81.8 %, 78.4 % and 66.7 % in the UHF and both MHF groups (p = 0.11). There was no statistical difference in BRFS and OS between the three groups. There was no grade 3 toxicity in UHF group compared to 0.7 % in 36 Gy and 5.1 % in 37.5 Gy groups. No difference was found in late GU and GI toxicities between groups.

[CONCLUSION] Our study confirms UHF with HDR-BB is safe for intermediate-risk prostate cancer, reducing treatment time and patient burden. Longer follow-up is needed to confirm results.