Post-marketing surveillance of radium-223 chloride in Japanese patients with castration-resistant prostate cancer with bone metastasis-final analysis of 3-year extended follow-up focusing on bone fractures.

Background: A post-marketing surveillance (PMS) study was conducted in Japan to assess real-world outcomes with radium-223 treatment in men with metastatic castration-resistant prostate cancer (mCRPC). Results from the treatment period showed that radium-223 was generally well tolerated. Follow-up was subsequently extended to 3 years to collect data on fracture events. Results of the extended follow-up are now reported.

Methods: This prospective, non-interventional, multicenter, single-cohort PMS study enrolled men with CRPC and bone metastases treated with radium-223 under clinical practice. Extended follow-up lasted until 3 years after the first administration of radium-223. Data on clinical fractures and survival were collected.

Results: A total of 334 patients were enrolled, with a median follow-up of 15.3 months (range 1-50). The overall incidence proportion of fractures reported as adverse events was 7.76% (95% confidence interval [CI] 5.09-11.25%), with a fracture incidence rate of 5.22 patients [with fracture]/100 person-years (PY). Patients who received bone-modifying agents (BMAs) had a numerically lower incidence of fractures (5.85%; 3.46/100PY vs 9.93%; 7.92/100PY). Median overall survival was 26.32 months (95% CI 21.65-not reached).

Conclusion: Compared with existing reference data, there was no obvious increase in the incidence of clinical fractures in Japanese patients with mCRPC who were treated with radium-223 under clinical practice. As is already well known for androgen deprivation, BMAs may also be useful in reducing bone fracture after radium-223.