Oncological outcomes post focal low‐dose‐rate brachytherapy in low‐intermediate risk prostate cancer

Objectives To prospectively evaluate oncological control, pathological progression, and its predictors following focal low‐dose‐rate (LDR) brachytherapy for low‐intermediate risk prostate cancer (PCa). Patients and methods LIBERATE is a prospective, multi‐centre clinical registry of patients who have undergone focal LDR brachytherapy for low‐intermediate risk PCa since September 2019 (ACTRN:12619001669189). Unifocal ISUP GG1 (≥10 mm in ≥1 core), GG2 (any length) or GG3 (longest core<10 mm) were included. Follow‐up entailed serial PSA measurements, and surveillance mpMRI and repeat transperineal prostate biopsy at 18–24 months post‐treatment. Pathological control was achieved on repeat biopsy if there was no cancer or ISUP GG1 in <10 mm of core or GG2–3 grade cancer with radiation treatment effect. Progression was defined as no pathological changes from baseline or tumour upgrading. Results Of 120 men enrolled, 55 (45.8%) have completed repeat histopathological assessments with a median (IQR) follow‐up of 38 (33–45) months. Pathological control was reported in 42 (76.4%) patients, including 25 negative biopsies, 12 clinically insignificant disease, and five in‐field ISUP GG2–3 with radiation treatment effect. Pathological progression was observed in 13 patients (23.6%), with concurrent clinically significant in‐ and out‐of‐field progression in three cases (5.5%) and isolated clinically significant out‐of‐field progression in 10 cases (18.2%). Five (9.1%) patients underwent salvage treatment, including three robotic‐assisted radical prostatectomies, one contralateral lobe LDR brachytherapy and one external beam radiation therapy. The salvage‐free survival at 1, 2, 3 and 4 years were 98.2%, 96.4%, 94.2% and 87.0%, respectively. Mean PSA velocity >0.55 ng/mL/year was a strong predictor of pathological progression (OR 23.54, 95% CI 4.28–129.35, p = 0.001), with a sensitivity of 76.9% and specificity of 90.5%. Conclusion With a median follow‐up of 38 months, these early results suggest that focal LDR brachytherapy for low‐intermediate risk, single‐lesion, imaging‐visible PCa demonstrates satisfactory oncological control. However, further follow‐up is needed to assess long‐term oncological outcomes.