Focal Salvage High Dose-Rate Brachytherapy for Locally Recurrent Prostate Cancer After Primary Radiation Therapy Failure: Results From a Prospective Clinical Trial

Abstract

Although increasing data support whole-gland salvage therapy for recurrent prostate cancer, toxicity remains a significant concern. We hypothesized that focal therapy, treating only a portion of the prostate containing recurrent disease, might be equally effective and associated with less toxicity. The objectives of this prospective study were to explore the toxicities, quality of life, and efficacy of focal salvage high-dose-rate (HDR) brachytherapy in patients with multiparametric magnetic resonance imaging (MRI)-visible, biopsy-confirmed local recurrence after previous definitive external beam radiation therapy. Fifteen patients with locally recurrent prostate cancer after external beam radiation therapy were enrolled in this prospective study. Patients were treated with ultrasound-based HDR brachytherapy with a prescription dose of 27Gy divided in 2 implants, separated by 1week, to the clinical target volume, which was defined as the quadrant of the prostate where the MRI-visible recurrent lesion was located. Toxicity, quality of life, and biochemical outcomes were analyzed. Postsalvage MRI was performed to assess radiation therapy response. Median follow-up was 36months. The median size of the recurrence on MRI was 9mm (range, 7-20mm), and clinical target volume at the time of HDR was 6.1mL (range, 2.2-16.1mL). Only one grade 3 genitourinary toxicity event was observed. No urinary retention was observed. Three-year prostate-specific antigen failure-free rate was 61%. There was no significant change in Expanded Prostate Cancer Index Composite urinary or bowel domains over time. Of the 14 patients who had a post-HDR MRI, 12 had a treatment response. Our results suggest that focal salvage HDR brachytherapy is well tolerated and promising. External validation is needed.