Utilization of androgen deprivation therapy (ADT) and stereotactic body radiation therapy (SBRT) for localized prostate cancer (PC) in the United States (US).

Abstract

370 Background: Randomized trials have demonstrated improved survival with the addition of ADT to conventionally fractionated radiotherapy (RT) for men with unfavorable intermediate risk (UIR) and high-risk (HR) prostate cancer (PC). The benefit of ADT with SBRT is unknown. The purpose of this study is to examine ADT utilization with SBRT in the US. Methods: Men > 40 years old with localized PC treated with external beam RT for curative intent between 2004-2015 were analyzed from the National Cancer Database. Patients who received brachytherapy, surgery, or lacked ADT or risk stratification data were excluded. A total of 7,559 men treated with SBRT (≥5Gy/fraction; ≤5 fractions; dose ≥25Gy) versus 133,825 men treated with moderate or conventional RT (≤3Gy/fraction; dose ≥60Gy) were included. Patients were stratified by risk: low (LR), favorable intermediate (FIR), UIR, and HR using NCCN criteria. Differences between RT and SBRT were determined via Chi-square test. Results: Among all PC treated with RT, SBRT use increased from 2004 to 2015 across risk groups – overall: 0.9% to 10.3%; LR: 0.9% to 21.6%; FIR: 1.1% to 13.7%; UIR: 0.6% to 10.8%; HR: 0.8% to 2.8%; p < 0.001. Among all PC treated with RT, ADT use declined from 2004 to 2015 for LR (22.8% to 5.5%), FIR (51.7% to 40.0%), UIR (53.4% to 49.5%), but not HR (78.9% to 84.2%); p < 0.001. Patients with EBRT were more likely to receive ADT compared to those with SBRT across risk groups (Table). Conclusions: The majority of patients receiving SBRT for UIR and HR disease in the US do not receive concurrent ADT, despite national guideline recommendations and the lack of level 1 evidence to support this practice pattern. The omission of ADT may result in inferior oncologic outcomes, and randomized trials are needed to establish the safety of omitting ADT with SBRT for higher risk PC.[Table: see text]