A comparative analysis of overall survival between high-dose-rate and low-dose-rate brachytherapy boosts for unfavorable-risk prostate cancer

PURPOSE: External beam radiation therapy (EBRT) with low-dose-rate (LDR) brachytherapy boost has been associated with improved biochemical progression-free survival and overall survival (OS) compared with dose-escalated EBRT (DE-EBRT) alone for unfavorable-risk prostate cancer. However, it is not known whether high-dose-rate (HDR) boost provides a similar benefit. We compare HDR boost against LDR boost and DE-EBRT with respect to OS. METHODS: Using the National Cancer Database, we identified 122,896 patients who were diagnosed with National Comprehensive Cancer Network intermediate- or high-risk prostate cancer between 2004 and 2014 and treated with DE-EBRT (75.6-86.4 Gy), LDR boost, or HDR boost. We compared the OS among the three groups using multivariable Cox proportional hazards regression. Inverse probability treatment weighting was used to adjust for covariate imbalance. RESULTS: On multivariable Cox proportional hazards regression, HDR boost was associated with a similar OS to LDR boost (adjusted hazard ratio [AHR] 1.03 [0.96, 1.11]; p = 0.38) but significantly better OS than DE-EBRT (AHR 1.36 [1.29, 1.44]; p < 0.001). Inverse probability treatment weighting analysis yielded similar results. There was no significant difference between LDR and HDR boosts for National Comprehensive Cancer Network intermediate-risk (AHR 1.05 [0.96, 1.15]; p = 0.32) and high-risk (AHR 1.00 [0.89, 1.12]; p = 0.98) subgroups (p-interaction = 0.55). CONCLUSIONS: Our results suggest that HDR brachytherapy boost yields similar OS benefits compared with LDR brachytherapy boost for unfavorable-risk prostate cancer. HDR boost may be a suitable alternative to LDR boost. (C) 2018 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.