Prior and concurrent use of abiraterone and enzalutamide with Ra-223 in an expanded access setting.

Abstract

253 Background: The aim of this prospective early-access program (EAP) was to monitor acute and long-term safety of Ra-223 CL2. The ALSYMPCA RA-223 phase III trial was completed prior to abiraterone (Abi) and enzalutamide (Enza) approval. Herein we provide experience with RA-223 in relationship to Abi and Enza. Methods: Symptomatic bone metastatic CRPC pts in the US who were ineligible for or had prior docetaxel were enrolled. Treatment included Ra-223 50 kBq/kg IV q4weeks for 6 cycles concomitant with standard of care medications. Analyses were conducted to assess safety and overall survival (OS) in pts with prior and concurrent Abi and Enza. Results: Of 184 treated, 120 (65%) had prior and 35 (19%) pts had concurrent Abi; 59 (32%) had prior and 25 (14%) pts had concurrent Enza. Baseline characteristics were generally balanced in the overall and across prior and concurrent groups. Pts with no concurrent Abi or Enza had a similar OS to the overall group (Abi 16m, Enza 17m, overall 17m). Due to a small number of events (7 Abi, 6 Enza), a median value was not calculated for the concurrent groups. 8 deaths occurred during treatment none were related to RA-223. The rate of Grade 3-5 AEs was similar across concurrent (Abi 37%, Enza 36%) and prior groups (Abi 43%, Enza 42%) vs overall 41%. Most frequently occurring Gr 3-4 events were anemia (Abi 17%, Enza 8%, overall 11%), thrombocytopenia (Abi 6%, overall 3%), and back pain (Enza 8%, overall 4%). Conclusions: In this EAP, Ra-223 concurrently administered with either abiraterone or enzalutamide was safe and well tolerated adding important information on concurrent use of RA-223 and hormonal agents. Clinical trial information: NCT01516762. [Table: see text]