Multicenter Analysis of Effect of High Biologic Effective Dose on Biochemical Failure and Survival Outcomes in Patients With Gleason Score 7–10 Prostate Cancer Treated With Permanent Prostate Brachytherapy

Purpose To investigate the biochemical control rates and survival for Gleason score 7–10 prostate cancer patients undergoing permanent prostate brachytherapy as a function of the biologic effective dose (BED). Methods and Materials Six centers provided data on 5,889 permanent prostate brachytherapy patients, of whom 1,078 had Gleason score 7 ( n = 845) or Gleason score 8–10 ( n = 233) prostate cancer and postimplant dosimetry results available. The median prostate-specific antigen level was 7.5 ng/mL (range, 0.4–300). The median follow-up for censored patients was 46 months (range, 5–130). Short-term hormonal therapy (median duration, 3.9 months) was used in 666 patients (61.8%) and supplemental external beam radiotherapy (EBRT) in 620 (57.5%). The patients were stratified into three BED groups: 220 Gy ( n = 234). Biochemical freedom from failure (bFFF) was determined using the Phoenix definition. Results The 5-year bFFF rate was 80%. The bFFF rate stratified by the three BED groups was 76.4%, 83.5%, and 88.3% ( p < 0.001), respectively. Cox regression analysis revealed Gleason score, prostate-specific antigen level, use of hormonal therapy, EBRT, and BED were associated with bFFF ( p < 0.001). Freedom from metastasis improved from 92% to 99% with the greatest doses. The overall survival rate at 5 years for the three BED groups for Gleason score 8–10 cancer was 86.6%, 89.4%, and 94.6%, respectively ( p = 0.048). Conclusion These data suggest that permanent prostate brachytherapy combined with EBRT and hormonal therapy yields excellent bFFF and survival results in Gleason score 7–10 patients when the delivered BEDs are >220 Gy. These doses can be achieved by a combination of 45-Gy EBRT with a minimal dose received by 90% of the target volume of 120 Gy of103 Pd or 130 Gy of125 I.