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

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.