Cardiovascular toxicities associated with abiraterone compared to enzalutamide-A pharmacovigilance study

Background: Androgen deprivation therapy (ADT) is standard-of-care for advanced prostate cancer. Studies have generally found increased cardiovascular risks associated with ADT, but the comparative risk of newer agents is under-characterized. We defined the cardiac risks of abiraterone and enzalutamide, using gonadotropic releasing hormone (GnRH) agonists to establish baseline ADT risk.

Methods: We used VigiBase, the World Health Organization pharmacovigilance database, to identify cardiac adverse drug reactions (ADRs) in a cohort taking GnRH agonists, abiraterone, or enzalutamide therapy for prostate cancer, comparing them to all other patients. To examine the relationship, we used an empirical Bayes estimator to screen for significance, then calculated the reporting odds ratio (ROR), a surrogate measure of association. A lower bound of a 95% confidence interval (CI) of ROR > 1 reflects a disproportionality signal that more ADRs are observed than expected due to chance.

Findings: We identified 2,433 cardiac ADRs, with higher odds for abiraterone compared to all other VigiBase drugs for overall cardiac events (ROR 1•59, 95% CI 1•48-1•71), myocardial infarction (1•35, 1•16-1•58), arrythmia (2•04, 1•82-2•30), and heart failure (3•02, 2•60-3•51), but found no signal for enzalutamide. Patients on GnRH agonists also had increased risk of cardiac events (ROR 1•21, 95% CI 1•12-1•30), myocardial infarction (1•80, 1•61-2•03) and heart failure (2•06, 1•76-2•41).

Interpretation: We found higher reported odds of cardiac events for abiraterone but not enzalutamide. Our data may suggest that patients with significant cardiac comorbidities may be better-suited for therapy with enzalutamide over abiraterone.

Funding: None.