Salvage High-Dose-Rate Brachytherapy for Localized Prostate Cancer Recurrence: A Comparative Analysis of Two Fractionation Schedules – Single-Institution Study of 223 Patients

Background Salvage high-dose-rate brachytherapy (sHDR-BT) is an efficient option for radiorecurrent prostate cancer. However, optimal fractionation and patient selection remain under discussion. Materials and Methods We retrospectively analyzed 223 patients treated with sHDR-BT between 2008 and 2021. Patients received either 3 × 10 Gy (n=150) or 2 × 13 Gy (n=73). Median follow-up was significantly longer in the 3 × 10 Gy group (125 vs 79 months, p<0.001). Apart from a higher frequency of high-grade disease (p=0.02) and nodal/distant recurrence (p<0.001) in the 2 × 13 Gy cohort, baseline characteristics were comparable between the groups. Kaplan–Meier estimator, log-rank test, and Cox proportional hazards models were used in statistical analysis. Results In the entire cohort, the 5-year overall survival rate exceeded 75%, and the median biochemical control was 12.6 years. Factors independently associated with worse oncological outcomes included primary ISUP grade 5, nodal or distant recurrence, castration resistance (CR), and shorter interval from primary therapy to recurrence. Use of androgen deprivation therapy (ADT) reduced the risk of local failure (p=0.04). Late genitourinary and gastrointestinal toxicity was acceptable and comparable between the subgroups (p=0.6 and p=0.4, respectively). In the no-ADT subgroup (n=83), median overall survival was 120 months, and median ADT-free survival reached 88 months. Conclusions Regardless of the fractionation schedule, sHDR-BT is an effective option for selected patients with localized, non-castration-resistant recurrence, characterized by relatively low toxicity. Castration resistance and regional or distant metastases strongly limit efficacy. In appropriately selected patients, salvage therapy can substantially delay the initiation of ADT.