Lack of Benefit from the Addition of External Beam Radiotherapy to Brachytherapy for Intermediate- and High-Risk Prostate Cancer

Publication date: Available online 31 July 2017
Source:International Journal of Radiation Oncology*Biology*Physics
Author(s): David D. Yang, Vinayak Muralidhar, Paul L. Nguyen, Ivan Buzurovic, Neil E. Martin, Kent W. Mouw, Phillip M. Devlin, Quoc-Dien Trinh, Peter F. Orio, Martin T. King
PurposeA recent randomized controlled trial demonstrated that the addition of external beam radiotherapy (EBRT) to brachytherapy did not improve progression-free survival in select patients with intermediate-risk prostate cancer. We evaluated whether the addition of EBRT to brachytherapy improves prostate cancer-specific mortality (PCSM) for intermediate- and high-risk disease using a large national database.Methods and MaterialsWe identified 5836 patients in the Surveillance, Epidemiology, and End Results-Medicare linked database diagnosed from 2004 through 2009 with National Comprehensive Cancer Network intermediate- (Gleason 7, prostate-specific antigen 10-20 ng/mL, or cT2b-T2c) or high-risk (Gleason 8-10 or prostate-specific antigen >20 ng/mL and ≤cT3a) prostate cancer and treated with brachytherapy, with or without EBRT and androgen deprivation therapy (ADT). Intermediate-risk patients with Gleason ≤3+4 and one intermediate-risk factor were considered favorable and all others unfavorable. We used multivariable Fine-Gray competing risks regression to study PCSM while adjusting for sociodemographic and clinical factors along with ADT use.ResultsOverall, the 50.3% of intermediate- and high-risk patients treated with brachytherapy and EBRT did not have a significantly improved PCSM compared to patients treated with brachytherapy alone (adjusted hazard ratio [AHR] 1.46, 95% CI 0.69-3.11, p=0.322; 5-year PCSM 2.4% vs. 1.0%). This lack of benefit was seen among favorable intermediate-risk (AHR 2.66, 95% CI 0.93-7.62, p=0.069; 1.3% vs. 0.6%), unfavorable intermediate-risk (AHR 0.68, 95% CI 0.16-2.96, p=0.612; 1.0% vs. 1.2%), and high-risk subgroups (AHR 1.82, 95% CI 0.67-4.98, p=0.242; 5.3% vs. 2.1%).ConclusionsThese results suggest that certain patients with intermediate- or high-risk prostate cancer treated with brachytherapy may not benefit from the addition of EBRT. A randomized controlled trial of brachytherapy plus ADT with or without EBRT for unfavorable intermediate- and favorable high-risk organ-confined prostate cancer should be undertaken.

Teaser

The efficacy of brachytherapy monotherapy for unfavorable-risk prostate cancer is unknown. Using a cohort of 5836 patients with intermediate- or high-risk disease treated with brachytherapy, we found the addition of external beam radiotherapy to not improve prostate cancer-specific mortality. This lack of benefit was observed for favorable intermediate-, unfavorable intermediate-, and high-risk subgroups. These results suggest that certain patients with unfavorable-risk disease treated with brachytherapy may not benefit from the addition of external beam radiotherapy.


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