Comparison of infection risk between enzalutamide and abiraterone in patients with prostate cancer

Background: Enzalutamide and abiraterone may differ in their immunomodulatory effects, and the prednisone coadministered with abiraterone can be immunosuppressive. This study aimed to compare the risk of different types of infection in patients with prostate cancer receiving enzalutamide or abiraterone in combination with androgen deprivation therapy. Methods: Patients with prostate cancer receiving enzalutamide or abiraterone in addition to androgen deprivation therapy in Hong Kong between December 1999 to March 2021 were identified in this retrospective cohort study and followed up until September 2021, death, or crossover. Outcomes, including any sepsis, pneumonia, urinary tract infection, cellulitis or skin abscess, central nervous system infections, and tuberculosis, were analyzed as both time-to-event outcomes (multivariable Fine-Gray regression, with mortality considered a competing event) and recurrent-event outcomes (multivariable negative binomial regression). Results: Altogether, 1582 patients were analyzed (923 abiraterone users; 659 enzalutamide users) with a median follow-up of 10.6 months (interquartile range: 5.3–19.9 months). Compared to abiraterone users, enzalutamide users had lower cumulative incidences of sepsis (adjusted subhazard ratio [SHR] 0.70 [0.53–0.93], p =.014), pneumonia (adjusted SHR 0.76 [0.59–0.99], p =.040), and cellulitis or skin abscess (adjusted SHR 0.55 [0.39–0.79], p =.001), but not urinary tract infection (adjusted SHR 0.91 [0.62–1.35], p =.643). Associations between exposure and central nervous system infections and tuberculosis were not assessed because of low event rates. Analyzing the outcomes as recurrent events gave similar results. Enzalutamide use may be associated with a lower risk of urinary tract infection in patients with diabetes mellitus. Conclusions: Compared to abiraterone users, enzalutamide users have significantly lower risks of sepsis, pneumonia, cellulitis, or skin abscess.