KEY POINTS
- This prospective phase II study treated 30 patients with biopsy-confirmed, MRI-visible local prostate cancer recurrence after prior external-beam radiotherapy. Median follow-up after salvage HDR brachytherapy was 72 months, providing unusually mature prospective follow-up for this setting.
- MRI-assisted ultrasound-guided treatment delivered 21 Gy to the whole prostate and 27 Gy to the MRI-defined recurrent intraprostatic target, divided across two implants separated by 1–2 weeks. No concurrent or adjuvant androgen-deprivation therapy was given.
- PSA progression-free survival was 73.0% at three years but only 24.8% at five years, with median biochemical recurrence-free survival of 44.1 months. Freedom from starting androgen deprivation remained 93.0% at three years and 69.6% at five years.
- Recurrence was frequently local despite the intraprostatic boost. 23/30 patients (77%) eventually experienced PSA relapse, and 18/23 relapsing patients (78%) had recurrent or persistent disease at the treated target documented by MRI, PSMA PET or targeted biopsy. Among 26 patients with post-treatment MRI, 9 (35%) already had persistent disease.
- Severe toxicity was uncommon: there was one grade 3–5 event among 30 patients (3.3%), a late grade 3 genitourinary toxicity, and no grade 3–5 gastrointestinal toxicity. Temporary urinary catheterization was required in 4 patients (13%).
- Grade 2 urinary symptoms were much more frequent than severe events: the authors report 86% acute and 70% late grade 2 urinary retention, partly reflecting routine alpha-blocker use. Patient-reported urinary and bowel quality-of-life domains showed an acute decline followed by recovery toward baseline during long-term follow-up.
- The efficacy estimate should be interpreted in the context of evolving staging: only 7/30 patients (23.3%) underwent PSMA PET staging and 77% entered before its routine introduction, so some patients may have harbored occult metastatic disease. The small cohort also cannot reliably quantify rare severe late events, and MRI-to-ultrasound fusion techniques evolved during accrual.
CLINICAL TAKEAWAY
Whole-gland salvage HDR brachytherapy with an MRI-defined boost can defer systemic therapy for selected men and produced remarkably little severe late toxicity. However, five-year biochemical control was poor with this two-fraction, no-ADT regimen, and frequent recurrence at the treated target argues for further work on dose, fractionation, patient selection and systemic therapy integration.