Deferred permanent prostate seed brachytherapy does not affect PSA outcome: results from a large retrospective cohort.

INTRODUCTION: To examine the outcome of deferred permanent seed brachytherapy (BT) for localized low or intermediate risk prostate cancer in order to identify predictors of delayed therapy (DT). MATERIALS AND METHODS: We studied 714 patients treated with BT with or without external radiotherapy. DT was defined as no treatment for > 350 days after the first biopsy with cancer. Factors influencing DT were analyzed. PSA outcome was assessed only in patients with a follow up ≥ 24 months. Patients with DT were compared to patients treated < 350 days using non-parametric tests. Multivariate analysis was performed using linear-regression analysis. RESULTS: BT was deferred in 125 patients (17.5%) for a median of 607 days (IQR 445-926). Patients with DT were older (71 years versus 69 years, p = 0.04) and had significantly less aggressive disease (percentage of positive biopsies, T1 disease, Gleason 6) on univariate analysis. On multivariate analysis, age (p = 0.01) and Gleason score (p = 0.05) were predictive for DT. Median (range) PSA follow up for DT patients was 36 months (24-78). The rate of patients with DT attaining a PSA at last follow up of < 0.2 ng/mL, < 0.5 ng/mL and ≤ 1 ng/mL was 53%, 73 % and 95%, respectively; only one patient (1.6 %) had biochemical failure (p = 0.61 compared to immediate BT). Multivariate analysis showed that age was predictive (p = 0.02) for a nadir of < 0.5 ng/mL and < 0.2 ng/mL (p = 0.017) and T-stage for a PSA < 0.2 ng/mL (p = 0.04). CONCLUSIONS: This is the largest analysis of the effects of deferred BT showing a promising rate of early PSA response.