ABSTRACT: Purpose:Six treatments have improved overall survival in men with metastatic castration-resistant prostate cancer (mCRPC), each differing in toxicities and cost. This study identified patient and provider factors associated with variation in treatment of men with mCRPC to identify potential barriers to treatments. Methods:A claims database of commercially insured patients was used to identify patients with prostate cancer treated with abiraterone, enzalutamide, docetaxel, cabazitaxel, sipuleucel-T, or radium-223 between 2010 and 2016. Multinomial and binomial logistic regressions were conducted to determine patient and provider factors associated with treatment patterns. Results:Among 5,575 patients identified, patients with a household income >$99,000 were less likely to receive an expensive oral androgen signaling inhibitor (abiraterone or enzalutamide) as first-line treatment versus docetaxel compared to patients with a household income <$50,000 (odds ratio, OR, 0.66, 95% confidence interval, CI, 0.48-0.92). Patients who are Black (OR 1.43, 95% CI 1.02-2.01), live in the Pacific region versus the South Atlantic (OR 2.68, 95% CI 1.74-4.11), received treatment from a urologist versus a medical oncologist (OR 16.05, 95% CI 6.01-42.86), or had pre-existing heart failure (OR 1.69, 95% CI 1.18-2.42) were more likely to receive first-line oral androgen signaling inhibitors over docetaxel, independent of other factors on multivariable analysis. Conclusion:Clinicians and policy makers should be aware of the potential barriers and provider factors that influence use of novel therapies among patients with advanced prostate cancer, including the paradoxical effect of income and the substantial effect of provider specialty on first-line treatment rendered to patients with mCRPC.