Low-dose-rate brachytherapy for prostate cancer: outcomes at >10 years of follow-up

To examine biochemical control, survival, and late morbidity with definitive low-dose-rate brachytherapy (LDR-BT) for patients with prostate cancer surviving for >10 years after treatment.

We identified 757 men with localised prostate cancer who underwent definitive LDR-BT in the period 1990-2006 and were followed for >10 years at our institution. Biochemical failure-free survival (BFFS), distant metastases-free survival (DMFS), prostate cancer-specific survival (PCSS), and overall survival (OS) were selected as study endpoints. Survival was examined using the log-rank test, Kaplan-Meier method, and Cox regression modelling. Urinary, quality of life (QoL), and potency scores at baseline and last follow-up were recorded.

The median follow-up was 12.5 years (range, 10.1-21.8 years). At the time of analysis, 88.6% of patients were alive, 1.5% died from prostate cancer and 13.9% developed biochemical failure, with 82% of failures occurring in the first decade of follow-up. Overall, 2.3% developed distant metastases. On multivariate analyses, stage T3a-T3b, prostate-specific antigen level of >20 ng/mL, intermediate- and high-risk disease predicted worse BFFS; whereas age >70 years at diagnosis and stage T3a-T3b predicted worse OS. A total biologically effective dose of ≥150 Gy and androgen-deprivation therapy were associated with improved BFFS, but not OS. The overall 17-year rates for BFFS, DMFS, PCSS, and OS were 79, 97, 97, and 72%, respectively. Respective 17-year BFFS rates for low-, intermediate- and high-risk patients were 86, 80, and 65% (P < 0.001), whereas OS rates for the same groups were 82, 73, and 60%, respectively (P = 0.09). Amongst those patients who were potent at baseline, 25% remained potent at the last follow-up. Urinary function and QoL were mainly unaffected.

LDR-BT yields excellent survival rates, with a 17-year PCSS rate of 97%. In all, 18% of patients with biochemical relapse failed at >10 years after implantation, which justifies their continued follow-up.