Real world utilization and disparities in outcome in the use of novel anti-androgen agents for metastatic prostate cancer.

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6616 Background: Despite advances in treatment, disparities exist in prostate cancer treatment and utilization of treatment resources based on several factors including race and socioeconomic status. As evidence-based guidelines increasingly define novel androgen receptor inhibitors (ARIs) as the standard of care, it is important to understand how the utilization of ARIs impacts the outcome. In this study, we investigated the relationship between the utilization of the two most commonly used ARIs, Abiraterone and Enzalutamide, and survival among patients with metastatic prostate cancer. Methods: We conducted a retrospective analysis of patients in the Surveillance, Epidemiology, and End Results (SEER)-Medicare database from January 1st, 2013 to December 31, 2017. All patients aged 18 years and above with metastatic prostate cancer were included. The objective of these study was to determine the utilization of ARIs in different groups (age, race, location, income status and marital status) and investigate the impact of these variables on the survival. Kaplan-Meir survival curves were used for the survival analysis. Patients were stratified by: who received an ARI alone or in combination vs. who did not. Log-rank tests were used to compare the stratified survival probability curves by groups. A multivariate proportional hazards model was used to compare the instantaneous risk of death in metastatic prostate cancer between patients based on selected covariates. All hypothesis tests were two-tailed with a p-value < 0.05 considered statistically significant. Results: A total of 5889 patients with metastatic prostate cancer were included in the analysis. The median age was 73 years; 39% of patients received an ARI alone or in combination with other agents. Among the patients who received ARIs, 77 %, 15% and 8% were white, black and of other races, respectively. Use of ARIs were more in urban locations (98.1% vs. 1.9% at rural locations) and in patients with higher and mid-level incomes (73.0% vs. 22.7% in low-income group). While survivals were inferior in all subgroups of patients who did not receive ARIs, survivals was better in white race (vs. black and others) as well as in younger age group who received ARIs. However, in the latter group, there was no statistical difference in survival in rural vs. urban locations and low income vs. high and mid-income groups. Conclusions: Our study shows that 39% of patients with metastatic prostate cancer in the SEER Medicare population utilized an ARI.There was a significant underutilization of ARIs in non-white, rural locations and low-income subgroup. White race and younger age populations were associated with better survival irrespective of use of ARIs. Among patients who did not receive ARIs, survivals were inferior in rural (vs. urban) and low-income (vs. high and mid-income) patients, but survivals were equivalent in these subgroups who received ARIs.