The following article features coverage from the European Society for Medical Oncology (ESMO) 2018 meeting. Click here to read more of Cancer Therapy Advisor‘s conference coverage.

Combining abiraterone acetate and prednisone (AAP) with radium-223 (Ra-223) failed to improve outcomes for men with chemotherapy-naive metastatic castration-resistant prostate cancer (CRPC) with bone metastases, according to results from a phase 3 study presented at the 2018 ESMO Congress in Munich, Germany.1

In fact, the combination increased the rate of fracture compared with treatment with AAP alone. Based on these results, study researchers recommended against combining Ra-223 with AAP in this patient population.

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The study included 806 men with asymptomatic or mildly symptomatic disease who were randomly assigned to receive AAP with (401 individuals) or without Ra-223 (405 individuals). The combination was being tested because AAP improves progression-free survival and overall survival in CRPC, and Ra-223 decreases symptomatic skeletal events (SSE) in CRPC with bone metastases.

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An increased rate of fractures and deaths in the combination arm led to early unblinding of the study. Median SSE-free survival was similar between patients assigned AAP plus Ra-223 and those assigned to AAP alone (22.3 vs 26.0 months; HR=1.22; 95% CI, 0.917-1.374). Median overall survival was also similar between the two study arms (30.7 vs. 33.3 months; H=1.195; 95% CI, 0.950-1.505).

Although survival outcomes were similar, about one-third (29%) of patients assigned to AAP plus Ra-223 had fractures compared with 11% of patients assigned AAP alone.

Men who were receiving bone health agents at baseline were allowed to continue taking them while on the study. Among these men, 15% assigned the combination regimen and 7% assigned to receive AAP alone had fractures compared with 37% and 15%, respectively, who were not taking bone health agents.

Disclosure: This study was sponsored by Bayer.

Read more of Cancer Therapy Advisor‘s coverage of the ESMO 2018 meeting by visiting the conference page.


  1. Smith MR. ERA 223: A phase 3 trial of radium-223 (RA-223) in combination with abiraterone acetate and prednisone/prednisolone for the treatment of asymptomatic or mildly symptomatic chemotherapy-naïve patients (pts) with bone-predominant metastatic castration-resistant prostate cancer (mCRPC). Abstract presented at: the ESMO 2018 Congress; Munich, Germany: October 20, 2018. Abstract LBA30.