Permanent prostate brachytherapy with or without supplemental external beam radiotherapy as practiced in Japan: outcomes of 1300 patients

Abstract

Purpose: To report outcomes for men treated with iodine-125 ((125)I) prostate brachytherapy (BT) at a single institution in Japan.

Methods and materials: Between 2003 and 2009, 1313 patients (median age, 68 years) with clinically localized prostate cancer were treated with (125)I BT. Median prostate-specific antigen level was 7.6 ng/mL (range, 1.1-43.3). T-stage was T1c in 60%, T2 in 39%, and T3 in 1% of patients. The Gleason score was <7, 7, and >7 in 49%, 45%, and 6% of patients, respectively. Neoadjuvant androgen deprivation therapy was used in 40% of patients and combined external beam radiotherapy of 45 Gy in 48% of patients. Postimplant dosimetry was performed after 30 days after implantation, with total doses converted to the biologically effective dose. Survival functions were calculated by the Kaplan-Meier method and Cox hazard model.

Results: Median followup was 67 months (range, 6-126). The 7-year biochemical freedom from failure for low-, intermediate-, and selected high-risk prostate cancers were 98%, 93%, and 81%, respectively (p < 0.001). Multivariate analysis identified the Gleason score, initial prostate-specific antigen level, positive biopsy rate, dose, and neoadjuvant androgen deprivation therapy as predictors for biochemical freedom from failure. The 7-year actuarial developing Grade 3+ genitourinary and gastrointestinal toxicity was 2% and 0.3%, respectively. Forty-four percent patients with normal baseline potency retained normal erectile function at 5 years.

Conclusions: (125)I prostate BT is a highly effective treatment option for low-, intermediate-, and selected high-risk prostate cancers. Side effects were tolerable. An adequate dose may be required to achieve successful biochemical control.

Keywords: Brachytherapy; Dose–response; Iodine-125; Low-dose-rate; Permanent seed implantation; Prostate cancer; Radiotherapy.