LAUSR

194Background: Abiraterone prolongs survival in patients with prostate cancer due to its potent inhibition of androgen synthesis. We previously observed increased rates of visceral metastatic disease at the time of progression on abiraterone compared to baseline, a poor prognostic feature associated with non-AR dependent prostate cancer. We hypothesized that the rate of development of visceral disease was increased with abiraterone compared to other treatments without potent androgen signaling inhibition. In order to test this, we examined time to visceral disease among patients treated with abiraterone vs placebo on the COU-AA-302 trial. Methods: We performed a post-hoc analysis of radiographic progression data for the phase 3 study of abiraterone vs placebo, via a data sharing agreement through the Yale Open Data Access Project. Data were censored at end of study treatment. The distribution of cumulative incidence for visceral metastases was calculated by the Kaplan-Meier method and compared with log-ra...