Clinical outcome with concurrent or layered treatment with radium-223 and abiraterone: A retrospective study of real-world experience with patients (pts) with metastatic castration-resistant prostate cancer (mCRPC).

Abstract

253 Background: Limited data exist on Ra-223 use in combination with Abi in a real-world setting. This retrospective study evaluated clinical outcomes in pts with mCRPC who received concurrent or layered Ra-223 + Abi treatment. Methods: This study used the Flatiron prostate cancer registry of electronic health records of pts with mCRPC treated with Ra-223 in US cancer clinics between 1/01/2013 and 6/30/2017. Two sub-cohorts were defined: pts treated with Ra-223 + Abi in a concurrent (both started within 30 days) or layered fashion (one of the two started over 30 days later). Descriptive analysis was done for baseline (BL) characteristics (prior to start of Ra-223), prior therapies, and clinical outcomes including skeletal-related events (SREs) and overall survival (OS). Results: 625 pts were treated with Ra-223; 136 (21.8%) received Ra-223 + Abi. Most received layered therapy (n = 97, 71%); concurrent start was less common (n = 39, 29%) [Table]. Conclusions: Prior to the start of Ra-223 therapy, half of the pts had prior SREs; almost one-fifth had prior pathologic fractures. Pts treated with Ra-223 + Abi had also received prior chemo and/or enzalutamide. SRE occurrence seems higher for concurrent treatment, but results should be cautiously interpreted due to low concurrent cohort size. OS in both cohorts exceeded the OS in the Phase III ALSYMPCA study (14.9 mo).[Table: see text]