Lack of Apparent Survival Benefit With Use of Androgen Deprivation Therapy in Patients With High-risk Prostate Cancer Receiving Combined External Beam Radiation Therapy and Brachytherapy

Abstract

Although level 1 evidence has demonstrated a survival benefit from the addition of androgen deprivation therapy (ADT) to external beam radiation therapy (EBRT) for patients with high-risk prostate cancer, the benefits of ADT with combined EBRT and brachytherapy for high-risk patients are unclear. We examined the association between ADT and overall survival in a national cohort of high-risk patients treated with EBRT with or without brachytherapy. We identified 46,325 men in the National Cancer Database with a diagnosis of high-risk prostate cancer (Gleason score 8-10, clinical stage T3-T4, or prostate-specific antigen >20ng/mL) who were treated with EBRT with or without brachytherapy and ADT from 2004 through 2011. Multivariable Cox regression analysis adjusting for sociodemographic and clinicopathologic factors was used to identify the association between ADT and overall survival. The median follow-up period was 48.6 and 59.2months for patients treated with EBRT only and combined modality RT, respectively. ADT was associated with an improvement in overall survival for the 85.0% (39,361) of the study cohort who underwent EBRT alone (adjusted hazard ratio 0.91, P=.001) but not for patients treated with combined modality RT (adjusted hazard ratio 1.05, P=.496), with a significant interaction (Pinteraction=.036). In contrast to the known survival benefit when ADT is given with EBRT, our results suggest that ADT might not improve survival for high-risk patients who undergo combined EBRT and brachytherapy. Given the significant adverse effects of ADT, in particular, with long-term therapy, a randomized controlled trial of combined EBRT and brachytherapy with or without ADT for select high-risk patients using a noninferiority design should be undertaken.