Salvage high-dose-rate brachytherapy for isolated seminal vesicle recurrence following definitive treatment for prostate cancer.

Purpose

Isolated seminal vesicle recurrence following definitive treatment for prostate cancer is uncommon and optimal management remains unclear. This study reports outcomes following salvage high-dose-rate (HDR) brachytherapy for isolated seminal vesicle relapse.

Methods

AND MATERIALS A retrospective analysis was conducted between January 2016 and August 2025 at the Mount Vernon Cancer Centre, Northwood, United Kingdom. Seminal vesicle recurrence was identified using multiparametric MRI (mpMRI) or Positron Emission Tomography (PET) imaging; nine patients also underwent biopsy confirmation. Interstitial HDR brachytherapy was delivered at 19 Gy in a single fraction or 26 Gy in two fractions. Outcomes included relapse-free survival (RFS), freedom from next treatment (FFNT), metastasis-free survival (MFS), overall survival (OS), and treatment-related toxicity.

Results

Twenty-two patients were treated with salvage HDR brachytherapy. Recurrence was confirmed radiologically in all patients; 82% of patients were staged using prostate-specific membrane antigen or Choline PET. Median follow-up was 68.3 months (range 4.7-116.2). RFS was 71.3% at 2 years and 40.5% at 2 and 5 years, respectively; 12 relapses (54.5%) occurred. Median time to subsequent therapy was 62.5 months (95% CI: 46.8-71.9 months). MFS was 89.7%, 83.7%, and 75.4% at 1, 3, and 5 years. OS was 95% at 1 and 3 years and 88% at 5 years. Five deaths occurred during follow-up. Four patients (18%) developed late grade ≥3 toxicity, including two grade 4 events.

Conclusions

Salvage HDR brachytherapy for isolated seminal vesicle recurrence provides meaningful disease control and may delay systemic therapy in selected patients, though toxicity risks require careful discussion. Longer interval between primary treatment and disease relapse, and a post-salvage PSA nadir of <0.2 ng/mL correlate with better outcomes.