e545 Background: Stereotactic body radiotherapy (SBRT) represents an emerging and cautiously guideline-approved definitive therapy option for prostate cancer, though long-term data on efficacy and toxicity is still pending. Herein, we sought to determine contemporary national SBRT trends and clinico-sociodemographic determinants associated with its use in prostate cancer. Methods: The National Cancer Data Base (NCDB) was queried to identify 181,544 patients diagnosed with localized prostate cancer from 2004-2012 who received external beam radiotherapy. Multivariable logistic regression adjusted for sociodemographic and clinical factors was used to identify independent determinants of SBRT use. Results: Rate of SBRT use for localized prostate cancer increased from 0.05% in 2004 to 4.87% in 2012 ( Ptrend< 0.001). SBRT was more likely to be delivered at academic centers, to patients with Medicare, and to patients who were white, younger, healthier, from wealthier and more educated zipcodes, and who had lower risk disease features (all P< 0.001). Relative to Whites, men from more affluent zipcodes, or men with low stage or grade prostate cancer, Blacks, Hispanics, and men from less affluent zipcodes and men with high stage or grade prostate cancer were less likely to receive SBRT after multivariable adjustment, with adjusted hazard ratios of 0.66, 0.35, 0.33, 0.07, and 0.21, respectively (all P< 0.001). Conclusions: The absolute national rate of SBRT use as definitive therapy for prostate cancer has increased nearly 100-fold over the last decade. Men who are White, younger, healthier, from more affluent zipcodes and with favorable disease characteristics are more likely to receive an emerging form of radiotherapy with unknown long-term efficacy and toxicity
