The time gap between Pd-103 prostate brachytherapy and supplemental beam radiation does not impact on rectal morbidity or likelihood of cure

Abstract

Objective: To determine whether treatment gap between supplemental beam radiation and brachytherapy implant affects rectal morbidity and likelihood of cure in the treatment of intermediate-risk prostate cancer.

Materials and methods: Five hundred sixty-eight patients with AJCC clinical stage T1c-T2a prostate cancer, Gleason score 7 to 9 and/or prostate-specific antigen (PSA) 10 to 20 ng/mL, were randomized to implantation with Pd-103 (90 vs. 115 Gy) with 44 Gy versus 20 Gy preimplant supplemental beam radiation, respectively. Treatment-related morbidity was monitored by mailed questionnaires, using a modified Radiation Therapy Oncology Group rectal morbidity criteria at 1, 3, 6, 12, 18, and 24 months. Patients who reported grade 1 or worse rectal morbidity were interviewed by telephone to clarify details regarding their rectal bleeding.

Results: Persistent rectal bleeding occurred in 36 of the 548 evaluable patients (7%). The mean gap among rectal bleeders was 3.8 days and among nonbleeders was 4.8 days (P = 0.236). Higher R100 and external beam dose of 44 Gy were significant predictors of rectal bleeding on univariate and multivariate analysis. Log-rank analysis did not demonstrate any improvement in biochemical failure free survival (BFFS) with shorter gap interval. On univariate analysis, Gleason score >7, PSA >10, D90 <100%, and treatment gap were all predictive of biochemical failure. On multivariate analysis, only Gleason score, PSA, and D90 remained significant predictors of BFFS.

Conclusion: Shorter gap intervals between supplemental beam radiation and brachytherapy implant are safe. Shorter gap intervals do not improve BFFS; however, they do allow for treatment completion in a more timely fashion.