Enzalutamide (ENZ) and Abiraterone Acetate (AA) are both first-line treatments for castration-resistant prostate cancer (CRPC). CRPC patients may switch from ENZ to AA or from AA to ENZ, if they do not respond well to the treatment, or experience intolerable side effects. This study examine treatment switching from ENZ to AA or from AA to ENZ, while investigating death as a competing risk. Whether ENZ compared to AA was associated with a longer time to starting oral opioids was also investigated.
An active comparator new-user design was used to identify 1406 men diagnosed with CRPC who received ENZ and AA using the Surveillance, Epidemiology, and End Results-Medicare Linked Database from 2012 to 2016. Inverse probability treatment weights (IPTW)-adjusted Fine-Gray competing risk models were used to compare the switching drugs and time-to-first use of oral opioids after initiating ENZ and AA.
Most patients (61 %) received AA, while 39 % received ENZ. Overall, ENZ demonstrated a significant reduction in the Sub-distribution Hazard Ratio (SHR) for switching treatment (IPTW-adjusted SHR 0.63; 95 % CI, 0.54-0.73; P < 0.001), indicating a decrease in treatment switching compared to AA. Cumulative incidence curves revealed substantial differences in switching patterns over time (Gray's test, p < 0.001). For time-to-first oral opioid use, the IPTW-adjusted SHR when comparing ENZ to AA was 0.95 (95 % CI, 0.83-1.09; P = 0.48), showing no significant difference between the two groups.
Patients who began their treatment with ENZ exhibited a substantially lower hazard of switching to AA when compared to those who started with AA.
Cancer epidemiology. 2025 Feb 12 [Epub ahead of print]
Ibrahim M Asiri, Ronald C Chen, Viraj Master, Lanyu Mi, Sarah E James, Folakemi T Odedina, Alan H Bryce, Jon C Tilburt, Irbaz B Riaz, Syed Arsalan Ahmed Naqvi, Veronica Abraham, Steven R H Beach, Ewan K Cobran
Saudi Food & Drug Authority, Department of Real-World Evidence, Riyadh, Saudi Arabia; Mayo Clinic College of Medicine and Sciences, Department of Quantitative Health Science, Scottsdale, AZ, United States., University of Kansas, School of Medicine, Department of Radiation Oncology, Kansas City, KS, United States., Emory University, School of Medicine, Department of Urology, Atlanta, GA, United States., Mayo Clinic College of Medicine and Sciences, Department of Quantitative Health Science, Scottsdale, AZ, United States., Mayo Clinic College of Medicine and Sciences, Department of Radiation Oncology, Phoenix, AZ, United States., Mayo Clinic College of Medicine and Sciences, Division of Hematology and Oncology, Jacksonville, FL, United States., City of Hope, Department of Medical Oncology & Therapeutics Research, Phoenix, AZ, United States., Mayo Clinic College of Medicine and Sciences, Department of Internal Medicine, Phoenix, AZ, United States., Mayo Clinic College of Medicine and Sciences, Department of Medicine, Phoenix, AZ, United States., American College of Medical Genetics and Genomic, Bethesda, MD, United States., University of Georgia, Franklin College of Arts and Sciences, Department of Psychology, Athens, GA, United States., Mayo Clinic College of Medicine and Sciences, Department of Quantitative Health Science, Scottsdale, AZ, United States. Electronic address: .