The role of external beam irradiation in patients undergoing prostate brachytherapy

Abstract The role of external beam irradiation (EBT) combined with transperineal interstitial permanent prostate brachytherapy (TIPPB) remain undefined. Therefore, the purpose of this study was to evaluate the role of EBT when combined with TIPPB in a retrospective, matched-pair analysis. Between September 1992 and January 1997, 605 consecutive patients with clinically localized prostate cancer underwent TIPPB. Patients with prostate specific antigen (PSA) levels ⩽10, Gleason scores ⩽6, and stage ⩽T2a underwent TIPPB alone using I-125 and Pd-103 [160 Gy (pre-TG-43) and 120 Gy, respectively]. Combined EBT and TIPPB was offered to patients with a PSA level >10 and/or Gleason score >6. From this cohort, a matched-pair analysis was performed to better assess the role of EBT and TIPPB (n = 215). PSA relapse-free survival was based on the American Society for Therapeutic Radiology and Oncology Consensus Panel definition. Kaplan-Meier actuarial survival curves were compared to assess various prognostic factors. The median follow-up for all 215 matched patients was 44 months (range, 24–81) with an actuarial PSA relapse-free survival (RFS) at 5 years of 81.1%. Patients treated with EBT and TIPPB had a 5-year PSA RFS of 83.5% whereas patients treated with TIPPB only had a 5-year PSA RFS of 79.4% (p = 0.715). There was no difference in outcome between groups with regard to Gleason score groupings or PSA ⩽10 ng/ml or >10 ng/ml. Risk group analysis combining PSA, Gleason score, and stage failed to identify any risk group for which the addition of EBT was significant. Analysis of postimplant dosimetry using the dose to 90% of the prostate volume (D90) failed to distinguish any difference between groups. A significant advantage for combining EBT and TIPPB could not be demonstrated in this retrospective matched-pair analysis. These data indicate that the role and rationale of combined treatment in prostate brachytherapy requires better clarification, with a prospective randomized trial.