Xofigo (radium-223 acetate) should NOT be used in combination with abiraterone acetate

In December last year we noted an announcement by Bayer that the company was unblinding data from an ongoing clinical trial because of a potential safety issue when radium-223 (Xofigo) was given in combination with abiraterone acetate + prednisone.

We now note that Bayer and the US Food and Drug Administration (FDA) have modified the prescribing information for Xofigo to state very clearly that this drug should not be administered to men with advanced forms of prostate cancer in combination with any form of abiraterone acetate (i.e., Zytiga or Yonsa) + prednisone or prednisolone

According to text in the updated and current prescribing information for Xofigo (see Sec. 5.2):

Xofigo is not recommended for use in combination with abiraterone acetate plus prednisone/prednisolone outside of clinical trials.

The clinical efficacy and safety of concurrent initiation of Xofigo treatment and abiraterone acetate plus prednisone/prednisolone treatment was assessed in a randomized, placebo-ontrolled multicenter phase 3 study (ERA-223 trial) in 806 patients with asymptomatic or mildly symptomatic castration resistant prostate cancer with bone metastases. The study was unblinded early based on an Independent Data Monitoring Committee recommendation.

At the primary analysis, an increased incidence of fractures (28.6% vs 11.4%) and deaths (38.5% vs 35.5%) have been observed in patients who received Xofigo in combination with abiraterone acetate plus prednisone/prednisolone compared to patients who received placebo in combination with abiraterone acetate plus prednisone/prednisolone. Safety and efficacy with the combination of Xofigo and agents other than gonadotropin-releasing hormone analogues have not been established.

While your sitemaster is sure that Bayer has probably already sent out relevant information to all physicians who might be expected to prescribe or supervise administration of one or other of these two agents in the management of advanced prostate cancer, this is also something that all support group leaders and other prostate cancer educators should be aware of.

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