Adverse Events Associated With Radium-223 in Metastatic Prostate Cancer: Disproportionality Analysis of FDA Data Reflecting Worldwide Utilization

Abstract

Background: Radionuclide radium-223 improves survival in men with metastatic castrate-resistant prostate cancer. The United States (US) Food and Drug Administration Adverse Events Reporting System (FAERS) is a post-market pharmacovigilance database valuable for adverse event (AE) assessments. We analyzed FAERS to identify disproportionate AE signals related to radium-223, and to explore radium-223's international utilization.

Materials and methods: We identified 2182 radium-223 cases associated with AE(s) from 2013 to 2018. The duration of radium-223 therapy was calculated. Reporting odds ratio (ROR) and proportional reporting ratio (PRR), with 95% confidence intervals (CIs), were calculated for AEs of interest. ROR shows disproportionate signals if the lower limit of the 95% CI > 1. PRR shows disproportionate signals if PRR ≥ 2, χ² statistic ≥ 4, and ≥ 3 AEs were reported. We identified any US Food and Drug Administration enforcement actions for radium-223.

Results: A majority (60.8%) of events occurred outside the US. Among patients with radium-223-associated AEs, the median therapy duration was only 56 days (corresponding to 2-3 treatment cycles). Disproportionate signals were detected for general health deterioration (ROR, 5.03; 95% CI, 4.23-5.98 and PRR, 4.94; 95% CI, 4.16-5.87), bone pain (ROR, 4.53; 95% CI, 3.67-5.59 and PRR, 4.48; 95% CI, 3.63-5.53), and hematologic AEs including anemia (ROR, 2.89; 95% CI, 2.55-3.27 and PRR, 2.80; 95% CI, 2.48-3.17), thrombocytopenia (ROR, 3.22; 95% CI, 2.77-3.74 and PRR, 3.16; 95% CI, 2.72-3.67), and pancytopenia/bone marrow failure (ROR, 4.83; 95% CI, 4.11-5.67 and PRR, 4.73; 95% CI, 4.03-5.55). There were no enforcement actions for radium-223.

Conclusions: Patients with metastatic castrate-resistant prostate cancer experiencing AEs are only receiving one-half the prescription dose of radium-223 required for survival benefit. Radium-223 is associated with health deterioration, bone pain, and hematologic AEs. Real-world analyses are important for ongoing radium-223 risk-benefit assessments.

Keywords: Disproportionality analysis; FAERS; Pharmacovigilance; Radium-223; Unsealed source radiotherapy.

Figure 1.

Radium-223 outcomes reported to FAERS, 2013Q2–2018Q2. There was a significant increase in raw number of cases reported to FAERS over time (Panel A); similar significant increases were seen in the raw number of the disability, hospitalization, and death outcomes. The slopes (β) indicate reports per quarter. Panel B shows the proportion of each outcome, by quarter.