The role of external beam radiotherapy with I-125/Pd-103 brachytherapy for prostate carcinoma.

BACKGROUND AND PURPOSE: To compare the biochemical outcomes of patients treated with Pd-103/I-125 brachytherapy alone vs. brachytherapy combined with external beam radiotherapy for early stage prostate carcinoma. METHODS: Brachytherapy monotherapy was used in 403 patients. Brachytherapy was combined with 45 Gy of external beam radiotherapy in 231 patients. Median follow-up was 58 months. To compare the biochemical outcomes of these two treatment approaches, patients were stratified into three relative risk groups: low risk, T(1)-T(2), Gleason 2-6/10, PSA< or =10.0; intermediate risk, T(3), Gleason 7-10/10, PSA>10.0 (one factor); high risk, T(3), Gleason 7-10/10, PSA>10.0 (two factors). RESULTS: The actuarial biochemical progression-free rate (bNED) for the entire 634 patients was 85% at 10 years. The bNED outcomes by risk group for monotherapy vs. combined therapy respectively were: low risk, 94 vs. 87%; intermediate risk, 84 vs. 85%; high risk, 54 vs. 62%. These differences did not reach statistical significance for any risk group. Rectal morbidity was slightly greater in the combined treatment patients. CONCLUSION: Although the addition of external beam irradiation to brachytherapy is conceptually appealing for patients with higher risk prostate carcinoma, we were unable to demonstrate a benefit. Whether this is because of patient selection biases within the risk groupings, an artefact of retrospective review, or because external radiotherapy does not offer additional benefit is uncertain.