Long-term outcome by risk factors using conformal high-dose-rate brachytherapy (HDR-BT) boost with or without neoadjuvant androgen suppression for localized prostate cancer

Abstract

Purpose The aim of this study is to analyze, during the prostate-specific antigen (PSA) era, the long-term outcome of patients treated with conformal high-dose-rate (HDR) brachytherapy boost to the prostate with or without androgen deprivation therapy (ADT) when patients are stratified by risk factors for failure. Methods and materials Between 1986 and 2000, 611 patients were treated for clinically localized prostate cancer in three prospective trials of external beam radiation therapy (EBRT) and dose-escalating HDR brachytherapy (BT) boost. There were 104 patients treated at Seattle, 198 at Kiel University, and 309 at William Beaumont Hospital. Of the 611 patients, 177 received a short course of neoadjuvant/concurrent ADT. The patients were divided into three risk groups. Group I, comprised of 46 patients, had stage ≤T2a, Gleason score (GS) ≤ 6, and initial PSA (iPSA) ≤ 10 ng/mL. Group II comprised 188 patients with stage ≥T2b, GS ≥ 7, and iPSA ≥ 10, with any one factor higher. Group III included 359 patients with any two risk factors higher. The American Society for Therapeutic Radiology and Oncology definition for biochemical failure was used. Results The mean follow-up was 5 years (range, 0.2–15.3). For the 611 patients, the 5-year and 10-year biochemical control (BC) rates were 77% and 73%, disease-free survival (DFS) was 67% and 49%, and cause-specific survival (CSS) was 96% and 92%, respectively. BC at 5 years for Group I patients was 96%, for Group II 88%, and for Group III patients 69%. CSS at 5 years was 100% in Group I, 99% in Group II, and 95% in Group III patients. In univariate and multiple regression analyses for BC, risk group, stage, iPSA, and GS were significant in predicting failure. However, age, follow-up interval, and ADT did not. Conclusions EBRT with HDR-BT produced excellent long-term outcomes in terms of BC, DFS, and CSS in patients with prostate cancer even for those at highest risk. Conformal HDR-BT is both a precise dose delivery system and an effective treatment for both favorable and unfavorable prostate cancer. The addition of a short course of neoadjuvant/concurrent ADT failed to improve outcome. The results were similar at all three institutions, giving credence to the reproducibility of the brachytherapy treatment.