KEY POINTS
- This retrospective single-institution study included 223 men receiving salvage HDR brachytherapy for prostate cancer recurrence after prior RT between 2008 and 2021. 150 received 3×10 Gy over 28–30 days and 73 received 2×13 Gy over 7–14 days.
- Whole-prostate salvage was used rather than focal treatment: the CTV encompassed the entire prostate and involved seminal vesicles where applicable, with no PTV expansion or dominant-lesion boost. The planning objective was CTV V100 ≥90%.
- Fractionation was not associated with biochemical control, local control, disease-free survival or distant metastasis-free survival in either univariable or multivariable analyses. Median biochemical control for the entire cohort was 151 months, and 5-year overall survival exceeded 75%.
- Disease biology mattered far more than whether patients received two or three fractions. Primary ISUP grade 5 predicted worse DFS (HR 8.66) and local control (HR 11.35), while castration resistance predicted worse DFS (HR 2.31), local control (HR 3.14) and distant metastasis-free survival (HR 3.78).
- Metastatic extent was similarly important: M1 disease at recurrence was associated with worse DFS (HR 3.90) and biochemical control (HR 3.74). In contrast, ADT use around salvage was associated with a lower local-failure risk (HR 0.47; p=0.01).
- Among 83 patients treated without peri-salvage ADT, median overall survival was 113 months, median ADT-free survival 88 months, and 54% remained ADT-free at five years. This subgroup was generally lower risk and should not be interpreted as evidence that ADT can routinely be omitted.
- Severe late toxicity was uncommon and similar between schedules. Late grade 3 GU toxicity occurred in 2.7% with 3×10 Gy versus 4.1% with 2×13 Gy, and grade 3 GI toxicity in 0.7% versus 2.7%; late toxicity differences were not statistically significant.
CLINICAL TAKEAWAY
For carefully selected patients with truly localized, hormone-sensitive radiorecurrent prostate cancer, salvage HDR brachytherapy can provide prolonged disease control with low rates of severe late toxicity. The lack of a clear outcome difference between 3×10 Gy and 2×13 Gy suggests that patient selection and disease biology may matter more than choosing between these two schedules.