PSOR9 Presentation Time: 12:10 PM: Utilization of Brachytherapy Boost in Men with Unfavorable Intermediate Risk Prostate Cancer Treated with Radiation Plus Androgen Deprivation Therapy

Abstract

<h3>Purpose</h3> Randomized data has shown a lower risk of recurrence with the addition of a brachytherapy (BT) boost in men with intermediate- and high-risk prostate cancer treated with external beam radiotherapy (EBRT) and concomitant androgen deprivation therapy (ADT). The inclusion of ADT with BT-based dose escalation is controversial, and professional guidelines support adding or excluding ADT for men with unfavorable intermediate risk prostate cancer treated with EBRT plus a BT boost. However, inclusion of ADT in men with intermediate risk prostate cancer may become more routine after results from RTOG 0815, and its impact on BT utilization in this population is unclear. Herein, we investigate the landscape of BT boost utilization in men with unfavorable intermediate risk prostate treated with EBRT and ADT in the United States. <h3>Materials and Methods</h3> Men ≥ 18 years diagnosed with clinical stage T1-2N0M0, PSA < 20, and Gleason grade group 3 prostate cancer between 2004-2017 were analyzed from the National Cancer Database. Those missing risk-stratification or treatment data were excluded. Eligible patients were grouped into the following cohorts based on primary radiation treatment modality: (i) EBRT alone or (ii) EBRT plus BT boost. EBRT monotherapy group received conventionally fractionated (1.8-2.0 Gy per fraction) ≥ 74 Gy or moderately hypofractionated (2.5-3.0 Gy per fraction) ≥ 60 Gy. EBRT plus BT boost group received conventionally fractionated ≥ 45 Gy or moderately hypofractionated ≥ 37.5 Gy, and either LDR or HDR BT. All patients received concomitant ADT. Cochran-Armitage was used to evaluate radiation modality treatment trends over time, and multivariable logistic regression was used to identify sociodemographic predictors of treatment. <h3>Results</h3> Among the eligible cohort, 46,490 (82%) were treated with EBRT alone and 10,236 (18%) were treated with EBRT plus BT boost. Median (range) age was 70 years (38-90). Between 2004 to 2017, there was a significant decline in annual use of a BT boost, from 24.5% in 2004 to 16.4% in 2017 (p<0.001). On MVA, Black race (adjusted OR 0.85, 95% CI 0.79-0.90, P<.0001), Medicaid insurance (aOR 0.67, 95% CI 0.57-0.78, P<.0001), and Charlson-Deyo comorbidity index > 1 (aOR 0.78, 95% CI 0.61-0.99, P=0.04) were associated with decreased odds of receiving a BT boost. Private insurance (aOR 1.11, 95% CI 1.05-1.18, P=.001), treatment at an academic institution (aOR 1.25, 95% CI 1.12-1.39, p<.0001), and Charlson-Deyo comorbidity index 0 (aOR 1.07, 95% CI 1.00-1.15, P=.04) were associated with increased odds of receiving a BT boost. <h3>Conclusions</h3> For men with unfavorable intermediate risk prostate cancer, utilization of a BT boost has significantly declined in the United States over the past two decades. Black and uninsured men have been at particularly high risk of undertreatment. Future studies aimed at identifying which men with intermediate-risk prostate cancer (e.g. based on genomic classifier or magnetic resonance imaging) derive the greatest oncologic benefit from a BT boost with EBRT and ADT is warranted to appropriately identify those who may be at risk of undertreatment with its exclusion. Additionally, future initiatives are needed to close the disparity gap in access and/or delivery of this efficacious treatment for Black and uninsured men, an overall undertreated population.