Urethra-sparing, intraoperative, real-time planned, permanent-seed prostate brachytherapy: toxicity analysis

To report the toxicity outcome in patients with localized prostate cancer undergoing (125)I permanent-seed brachytherapy (BT) according to a urethra-sparing, intraoperative (IO), real-time planned conformal technique.

Data were analyzed on 250 patients treated consecutively for low- or intermediate-risk prostate cancer between 2005 and 2009. The planned goal was urethral V(150) = 0. Acute and late genitourinary (GU), gastrointestinal (GI), and erectile toxicities were scored with the International Prostate Symptom Score (IPSS) questionnaire and Common Terminology Criteria for Adverse Events (version 3.0). Median follow-up time for patients with at least 2 years of follow-up (n = 130) was 34.4 months (range, 24-56.9 months).

Mean IO urethra V(150) was 0.018% ± 0.08%. Mean prostate D(90) and V(100) on day-30 computed tomography scan were 158.0 ± 27.0 Gy and 92.1% ± 7.2%, respectively. Mean IPSS peak was 9.5 ± 6.3 1 month after BT (mean difference from baseline IPSS, 5.3). No acute GI toxicity was observed in 86.8% of patients. The 3-year probability of Grade ≥2 late GU toxicity-free survival was 77.4% ± 4.0%, with Grade 3 late GU toxicity encountered in only 3 patients. Three-year Grade 1 late GI toxicity-free survival was 86.1% ± 3.2%. No patient presented Grade ≥2 late GI toxicity. Of patients with normal sexual status at baseline, 20.7% manifested Grade ≥2 erectile dysfunction after BT. On multivariate analysis, elevated baseline IPSS (p = 0.016) and high-activity sources (median 0.61 mCi) (p = 0.033) predicted increased Grade ≥2 late GU toxicity.

Urethra-sparing IO BT results in low acute and late GU toxicity compared with the literature. High seed activity and elevated IPSS at baseline increased long-term GU toxicity.