Prostate high dose-rate brachytherapy as monotherapy for low and intermediate-risk prostate cancer: Efficacy results from a randomized phase II clinical trial of one fraction of 19 Gy or two fractions of 13.5 Gy: A 9-year update.

High dose-rate (HDR) brachytherapy as a monotherapy is an accepted treatment for localized prostate cancer, but the optimal dose and fractionation schedule remain unknown. We report on the efficacy of a randomized Phase II trial comparing HDR monotherapy delivered as 27 Gy in 2 fractions vs. 19 Gy in 1 fraction with a median follow-up of 9 years.

Enrolled patients had low or intermediate-risk disease, <60 cc prostate volume and no androgen deprivation use. Patients were randomized to 27 Gy in 2 fractions delivered one week apart vs a single fraction of 19 Gy.

170 patients were randomized: median age 65 years, median follow-up 107 months and median baseline PSA 6.35 ng/ml. NCCN risk categories comprised low (19 %), favourable (51 %), and unfavourable intermediate risk (30 %). The median PSA at 8 years was 0.08 ng/ml in the 2-fraction arm vs. 0.89 ng/ml in the single-fraction arm. The cumulative incidence of local failure at 8 years was 11.2 % in the 2-fraction arm vs. 35.9 % in the single-fraction arm (p < 0.001). The incidence of distant failure at 8 years was 3.8 % in the 2-fraction arm and 2.5 % in the single-fraction arm (p = 0.6).

HDR monotherapy delivered in two fractions of 13.5 Gy demonstrated a persistent cancer control rate at 8 years and was well-tolerated. Single-fraction monotherapy yielded poor oncologic control and is not recommended. These findings contribute to the ongoing discourse on optimal HDR monotherapy strategies for low and intermediate-risk prostate cancer.

Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology. 2024 Jun 13 [Epub ahead of print]

John M Hudson, Andrew Loblaw, Merrylee McGuffin, Hans T Chung, Chia-Lin Tseng, Joelle Helou, Patrick Cheung, Ewa Szumacher, Stanley Liu, Liying Zhang, Andrea Deabreu, Alexandre Mamedov, Gerard Morton

Sunnybrook Odette Cancer Centre, University of Toronto, Canada., Sunnybrook Odette Cancer Centre, University of Toronto, Canada. Electronic address: .