Role of external beam radiotherapy with low-dose-rate brachytherapy in treatment of prostate cancer

Objectives. To report a single-institution experience and analysis of the role of supplemental external beam radiotherapy (EBRT) with brachytherapy. EBRT is often used in addition to low-close-rate brachytherapy in the treatment of prostate cancer, particularly for disease with adverse features. Methods. A cohort of 189 consecutive patients, who had undergone low-close-rate brachytherapy at our institution and who had demographic, disease, and treatment information and a minimum of 2 years of follow-up available, constituted the study group. This cohort was divided into two major groups according to the use of supplemental EBRT. Using two successive prostate-specific antigen rises greater than 1 ng/mL as the definition of failure, biochemical failure-free survival curves were constructed for the EBRT and no-EBRT groups and compared using the log-rank test. Additionally, a multivariate analysis of all major disease and treatment factors was performed using the Cox proportional hazards model. Results. Despite the greater proportion of adverse disease factors in the EBRT group, the 5-year biochemical failure-free survival rate in the EBRT versus no-EBRT groups was 80% versus 59%, respectively (P < 0.01). On multivariate analysis, the only factor reaching significance in predicting biochemical control was the use of EBRT (P = 0.043). Conclusions. In our study, the addition of EBRT conferred a significant biochemical control advantage when added to low-close-rate brachytherapy. Because our study was not designed to permit detailed subset analyses, more work is needed to determine the precise brachytherapy population that will benefit from this use of supplemental EBRT.