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

To prospectively evaluate oncological control, pathological progression, and its predictors following focal low-dose-rate (LDR) brachytherapy for low-intermediate risk prostate cancer (PCa).

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.

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%.

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.