Direct 2-arm comparison shows benefit of high-dose-rate brachytherapy boost vs external beam radiation therapy alone for prostate cancer

PURPOSE: To evaluate the outcomes of patients treated for intermediate- and high-risk prostate cancer with a single schedule of either external beam radiation therapy (EBRT) and high-dose-rate brachytherapy (HDRB) boost or EBRT alone. METHODS AND MATERIALS: From 2001-2006, 344 patients received EBRT with HDRB boost for definitive treatment of intermediate- or high-risk prostate cancer. The prescribed EBRT dose was 46 Gy in 23 fractions, with a HDR boost of 19.5 Gy in 3 fractions. This cohort was compared to a contemporaneously treated cohort who received EBRT to 74 Gy in 37 fractions, using a matched pair analysis. Three-dimensional conformal EBRT was used. Matching was performed using a propensity score matching technique. High-risk patients constituted 41 of the matched cohorts. Five-year clinical and biochemical outcomes were analyzed. RESULTS: Initial significant differences in prognostic indicators between the unmatched treatment cohorts were rendered negligible after matching, providing a total of 688 patients. Median biochemical follow-up was 60.5 months. The 5-year freedom from biochemical failure was 79.8 (95 confidence interval [CI], 74.3 -85.0 ) and 70.9 (95 CI, 65.4 -76.0 ) for the HDRB and EBRT groups, respectively, equating to a hazard ratio of 0.59 (95 CI, 0.43-0.81, P=.0011). Interaction analyses showed no alteration in HDR efficacy when planned androgen deprivation therapy was administered (P=.95), but a strong trend toward reduced efficacy was shown compared to EBRT in high-risk cases (P=.06). Rates of grade 3 urethral stricture were 0.3 (95 CI, 0 -0.9 ) and 11.8 (95 CI, 8.1 -16.5 ) for EBRT and HDRB, respectively (P