Functional outcomes and toxicity following focal low‐dose‐rate brachytherapy for low–intermediate risk prostate cancer

Objectives: We aim to prospectively evaluate functional outcomes and toxicity following focal low-dose-rate (LDR) brachytherapy for low-intermediate risk prostate cancer (PCa). Patients and Methods: LIBERATE is a clinical registry of men treated with focal LDR brachytherapy for low-intermediate risk PCa since September 2019. Follow-up occurred at 6 weeks and every 3 months thereafter. Outcomes were assessed using validated patient-reported outcome measures (PROMs): IPSS, Expanded PCa Index Composite (EPIC) Bowel Assessment, and International Index of Erectile Function (IIEF-5). Adverse events (AEs) were clinically graded per Common Terminology Criteria for Adverse Events v5.0. Minimal important differences (MIDs) were defined as ±3.1 for IPSS, ±5 for EPIC bowel domain, and ±4 for IIEF-5. Results: Of 120 patients enrolled, 88/120 (73.3%) had ≥12 months follow-up, and 79/88 (89.7%) completed PROMs with a median (IQR) follow-up of 33 (26-41) months. At 6 weeks, a transient, statistically and clinically significant increase in IPSS was observed, which returned to baseline by 12 months (median IPSS: 6 at baseline, 12 at 6 weeks, 6 at 12 months). EPIC bowel scores showed no significant changes, with 72 (91.1%) patients having rectal spacer. Among 66 sexually active men, 40 (60.6%) had no or mild erectile dysfunction (ED) at baseline, with a median IIEF-5 score of 22.5, decreasing to 22 at 6 weeks and plateauing at 21 at 6 months, none meeting MID criteria. For the 26 patients with mild to severe ED at baseline, the median IIEF-5 score declined from 10 at baseline to 5 at 6 months, with partial recovery followed by a drop to 5.5 at 2.5 and 3 years. Declines at 6 months and beyond 2 years were both statistically and clinically significant. No Grade ≥3 AEs were reported. Conclusion: Focal LDR brachytherapy is associated with favorable functional outcomes and minimal toxicity. Further studies are required to evaluate long-term results.