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

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).

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.

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).

This is the largest analysis of the effects of deferred BT showing a promising rate of early PSA response.