Mid‐term outcome of permanent prostate iodine‐125 brachytherapy in J apanese patients

Objectives To analyze mid‐term oncological outcomes of low‐dose rate brachytherapy in J apanese patients. Methods Between 2003 and 2010, 604 consecutive patients with clinically localized prostate cancer were treated with low‐dose rate brachytherapy at J ikei U niversity H ospital in Tokyo, Japan. Median follow up was 48 months. Of these patients, 260 (43%) were treated with neoadjuvant therapy, 45 (7.5%) with adjuvant hormonal therapy and 75 (12.4%) with supplemental external beam radiation therapy. Biochemical recurrence was defined as the prostate‐specific antigen nadir plus 2 ng/mL. Results Of the 604 patients, 219 (36.2%) were low risk, 361 (59.8%) were intermediate risk and 24 (4.0%) had high‐risk disease. The median biologically effective dose was 174.4  G y2. At 8 years, biochemical recurrence‐free survival, cancer‐specific survival, and overall survival were 82.2%, 100% and 95.6%, respectively. Biochemical recurrence‐free survival at 8 years was 89.9%, 79.4% and 52.5%, for the low‐, intermediate‐, and high‐risk groups, respectively. Biochemical recurrence‐free survival for the high‐risk group was significantly lower than the low‐ and intermediate‐risk groups ( P  < 0.001). Biochemical recurrence‐free survival did not differ significantly by biologically effective dose stratification. In multivariate analysis, younger age ( P  = 0.045), higher prostate‐specific antigen ( P  = 0.004), higher G leason score ( P  = 0.006) and higher clinical T  stage ( P  = 0.008) were significant covariates associated with biochemical recurrence. The addition of hormonal therapy or external beam radiation therapy was associated with significantly better outcomes than low‐dose rate brachytherapy monotherapy ( P  = 0.0021 and 0.010). Just four patients experienced G 3 genitourinary or gastrointestinal toxicity. Conclusions Low‐dose rate brachytherapy results in excellent mid‐term oncological outcomes and acceptable toxicity in J apanese patients. In our experience, biologically effective dose does not represent a significant predictor for biochemical recurrence.