KEY POINTS
- This single-centre retrospective series included 22 patients with isolated seminal vesicle recurrence after previous definitive prostate cancer treatment. Median follow-up after salvage was 68.3 months, and PET was used in 82% to exclude more extensive disease.
- Salvage HDR brachytherapy was delivered using transperineal interstitial implantation with MRI-based planning. 17 treatment episodes used 19 Gy ×1, while six used 26 Gy in 2 fractions, the latter introduced later because of concerns about single-fraction HDR efficacy.
- Target coverage was high with both schedules. Median PTV V100 was 100% with 19 Gy ×1 and 99.9% with 26 Gy/2, while rectal and urethral dose metrics remained within institutional protocol constraints.
- Median relapse-free survival was 39 months. RFS was 71.3% at 2 years and 40.5% at 5 years, while 12/22 patients ultimately relapsed.
- The treatment meaningfully delayed additional therapy in some patients: median time to the next treatment was approximately 62.5 months. Five-year metastasis-free survival was 75.4%, and five-year overall survival was 88%.
- Failure was frequently not where the salvage implant had been delivered. Among 12 relapses, 75% included out-of-field disease, suggesting that occult disease remained an important limitation even after modern imaging-based selection.
- Late toxicity was clinically significant. Four patients (18%) developed grade ≥3 GU toxicity, including two urethral strictures, one recto-urethral fistula and one urinary diversion; the fistula and diversion were grade 4 events and occurred in heavily previously irradiated patients.
CLINICAL TAKEAWAY
For carefully selected patients with genuinely isolated seminal vesicle recurrence, focal HDR brachytherapy can provide several years without systemic therapy and preserve a potentially curative local-salvage strategy. The trade-off is meaningful late GU toxicity, particularly after substantial prior pelvic irradiation, and the high proportion of out-of-field failures underscores how critical patient selection remains.