Assessing the impact of brachytherapy boost and androgen deprivation therapy on survival outcomes for patients with unfavorable intermediate-risk prostate cancer patients treated with external beam radiotherapy

BACKGROUND: Current recommendations regarding radiotherapy treatment for unfavorable intermediate-risk prostate cancer (UIR-PCa) include external beam radiotherapy (EBRT) +/- brachytherapy boost (BT) +/- androgen deprivation therapy (ADT). The ideal radiotherapy treatment approach for UIR-PCa has not been well-defined. We hypothesized that EBRT + BT +/- ADT is associated with improved overall survival (OS) relative to EBRT +/- ADT in men with UIR-PCa. MATERIALS AND METHODS: The National Cancer Database (NCDB) was used to retrospectively identify 32,246 men diagnosed between 2004 and 2015 with UIR-PCa who received EBRT ( n = 13,265), EBRT +ADT ( n = 13,123), EBRT + BT ( n = 3440), or EBRT + BT +ADT ( n = 2418). OS was the primary outcome. Inverse probability of treatment weighting was used to adjust for covariable imbalances and weight-adjusted multivariable analysis using Cox regression modeling was used to compare OS hazard ratios. RESULTS: Median follow-up was 60 months (range: 3-168 months). EBRT +ADT correlated with improved OS relative to EBRT alone on multivariable analysis (Hazard Ratio (HR): 0.92, [95% Confidence Interval: 0.87-0.98], p = 0.005). Compared to EBRT +ADT, EBRT + BT (HR: 0.77 [0.69-0.85], p = 3 x 10(-7)) and EBRT + BT +ADT (HR: 0.75 [0.67-0.83], p = 6 x 10(-8)) were associated with improved OS. Eight-years OS for the EBRT +ADT versus EBRT + BT +ADT was 70% and 78% ( p < 0.0001), which is similar to historical clinical trials (ASCENDE-RT 9-year OS: 74% vs. 78%, p = 0.29). Relative to EBRT + BT, EBRT + BT +ADT was not associated with improved OS (HR: 0.99 [0.87-1.11], p = 0.82). CONCLUSIONS: In a large retrospective cohort, the addition of brachytherapy to EBRT correlated with improved survival in men with UIR-PCa. Men receiving EBRT +ADT + BT had improved OS relative to EBRT +ADT. The addition of ADT to EBRT, but not to EBRT + BT, correlated with improved OS. (C) 2022 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.