Observation of CNS events in real-world use of enzalutamide (ENZ) and bicalutamide (BIC).

Abstract

235 Background: TERRAIN, a randomized, double-blind, multi-center, phase II trial compared efficacy and safety of ENZ to BIC in men with mCRPC. Although ENZ and BIC fall within the same drug classification, rates of seizure and other central nervous system (CNS) events, observed in non-clinical trial populations have not been explored. The objective of this study was to compare rates of real world CNS events in patients treated with ENZ or BIC. Methods: Retrospective claims from Truven Health MarketScan database were used to identify patients with a PC diagnosis; ≥1 claim for ENZ or BIC (index date) after 9/1/2012; > 6 months of continuous eligibility prior to index date (baseline period) and no use of ENZ or BIC prior to index. Patients were followed until 12/2014 or loss to follow-up. Patients were excluded if they had a CNS condition or another cancer diagnosis during the baseline period. CNS conditions were defined as a diagnosis for amnesia or memory impairment, anxiety, ataxia, cognitive disorders, confusion, convulsions, disturbance in attention, dizziness, falls, fatigue/asthenia, hallucinations, headaches, insomnia, pain, paresthesia, seizures, weakness, or other CNS disorders. Kaplan-Meier (KM) survival curves were used to compare the KM rates of developing any CNS conditions between patients who initiated ENZ relative to patients who initiated BIC. A subgroup analysis of patients with metastatic disease was performed. Results: The table below compares the development of CNS conditions between ENZ and BIC patients. Conclusions: This study shows that rates of CNS events are significantly higher in patients initiating ENZ as compared to BIC, even when controlling for metastatic status. [Table: see text]