Fracture risk and survival outcomes in metastatic castration-resistant prostate cancer (mCRPC) patients (pts) sequentially treated with abiraterone acetate (AA) and radium-223 (RA223).

Abstract

e17593 Background: The increased incidence of bone fractures found in pts who received the AA-RA223 combination compared to those treated with AA alone in the ERA223 trial led to restrictive recommendations by the European Medicines Agency which limited the use of RA223 to pts who have received at least two previous treatments for mCRPC or who cannot receive any other treatment. Moreover, clinicians started to debate the risk of RA223-related fractures associated with the sequential administration of AA and RA223. The aim of this retrospective study was to assess the safety of administering RA223 to pts who have progressed during AA treatment mainly in terms of the rate of skeletal fractures. Methods: We retrospectively reviewed the records of mCRPC pts who received RA223 after progressing during an AA treatment line in everyday clinical practice in ten Italian Hospitals. Results: We reviewed data of a consecutive series of 94 mCRPC pts. Most of the pts (85.1%) received RA223 as second- or third-line treatment and had a Soloway score 2 or 3 (90%). RA223 treatment was well-tolerated: there were only four cases of grade 3 anemia, two case of grade 3 leukopenia, and one case of grade 3 neutropenia. The overall fracture rate of 2.1%: one fracture was recorded during the course of RA223 treatment, and one was recorded one month after its end. The fractures both occurred at metastatic sites in pts who were not treated with antiresorptive agents. Median overall survival (OS) from RA223 start was more than 14 mos and the pts who received Ra223 in second line (which is not allowed today in Europe) had the same median OS as those who received this agent in later lines. Conclusions: The findings of this study showed that the treatment with RA223 as subsequent treatment line after AA was active and safe with a very low risk of a fracture. The OS outcomes indicated that the administration of RA223 in early treatment lines is not detrimental, even after AA. Thus the present observational report makes a valuable contribution to the current debate concerning the risks and benefits of including RA223 in the therapeutic algorithm.