The Potential of Radium-223 in Modern Prostate Cancer Treatment
More evidence may be needed to understand the safety and efficacy of radium-223 in combination with abiraterone or enzalutamide.
The majority of patients with metastatic castration-resistant prostate cancer (CRPC) have evidence of bone metastases. Among available bone-targeted therapies, only radium-223 dichloride (radium-223), a targeted alpha emitter that binds to areas of increased bone turnover in metastases, has been shown to improve survival rates.
The phase 3 ALSYMPCA trial (ClinicalTrials.gov Identifier: NCT00699751) showed that radium-223 increased overall survival by more 3 months compared with placebo among patients with metastatic CRPC and bone metastases (14.9 months vs 11.3 months; P < .001).1 Based on these results, the US Food and Drug Administration (FDA) approved radium-223 in 2013 for patients with CRPC, symptomatic bone metastases, and no known visceral metastatic disease.
Yet according to Oliver Sartor, MD, medical director of Tulane Cancer Center in New Orleans, Louisiana, there is some controversy about which patients would benefit most from the use of radium-223 in today's treatment landscape.
“Radium-223 was developed in the context of older therapies that are not commonly used today,” Dr Sartor explained. “The current FDA approvals [for these patients] include agents such as abiraterone and enzalutamide, but in the ALSYMPCA trial there was no utilization of these agents.”
Dr Sartor and colleagues recently published the results of a phase 2, single-arm study that evaluated the use of radium-223 in an expanded access program (EAP) that provided early access to radium-223 after the positive results from ALSYMPCA, but before commercial availability of the drug.2 This study was the first US experience with the combination of radium-223 and these agents.
The study included 252 patients with symptomatic metastatic CRPC and 2 or more bone metastases. Of the enrolled patients, 184 received radium-223 55 kBq/kg intravenously every 4 weeks for 6 cycles. The median overall survival was 17 months, and a post hoc analysis showed that radium-223 was safe regardless of patients' concurrent use of abiraterone or enzalutamide.