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Evaluation

Oral Presentation

Session: Navigating the Cancer Landscape Using Innovative Pharmacoepidemiologic Methods

Comparative effectiveness and cardiovascular safety of enzalutamide versus abiraterone amongst older U.S. men diagnosed with metastatic castration-resistant prostate cancer

Tuesday, August 27, 2024

1:45 PM – 2:00 PM CEST

Location: Room II

Presenting Author(s)

Charles E. Gaber, PhD, MPH (he/him/his)

Assistant Professor
Department of Pharmacy Systems, Outcomes and Policy, University of Illinois Chicago, Chicago, IL, USA, United States

Slides

Co-Author(s)

EO

Ebere Okpara, BPharm

Department of Pharmacy Systems, Outcomes and Policy, University of Illinois-Chicago College of Pharmacy, Chicago, IL, USA, United States
AA

Abdullah I. Abdelaziz, BPharm, MS

Department of Pharmacy Systems, Outcomes and Policy, University of Illinois-Chicago College of Pharmacy, Chicago, IL, USA
Chicago, United States
Jyotirmoy Sarker, MPharm, MBA, MBiotech

Research Assistant, PhD Candidate
University of Illinois Chicago, Department of Pharmacy Systems, Outcomes and Policy
Chicago, United States
KH

Kent A. Hanson, PharmD

Department of Pharmacy Systems, Outcomes and Policy, University of Illinois-Chicago College of Pharmacy, Chicago, IL, USA
Chicago, United States
LH

Lubna Hassan, PharmD

Department of Pharmacy Systems, Outcomes and Policy, University of Illinois-Chicago College of Pharmacy, Chicago, IL, USA
Chicago, United States
FL

Fang-Ju Lin, PhD, MS

1 Department of Pharmacy Systems, Outcomes and Policy, University of Illinois-Chicago College of Pharmacy, Chicago, IL, USA
Chicago, United States
TL

Todd A. Lee, PharmD, PhD

Department of Pharmacy Systems, Outcomes and Policy, University of Illinois Chicago, United States
NR

Natalie Reizine, MD

Division of Hematology & Oncology, Department of Medicine, University of Illinois-Chicago College of Medicine, Chicago, IL, USA
Chicago, United States

Background: Enzalutamide and abiraterone are two androgen receptor signaling inhibitors used in the treatment of metastatic castration-resistant prostate cancer (mCRPC). To date, no randomized trials have compared the effectiveness and safety of these medications head-to-head, and observational data are limited.

Objectives: To compare real-world overall survival and risk of major adverse cardiovascular events (MACE) between initiators of abiraterone and enzalutamide in a cohort of older adult men diagnosed with mCRPC.

Methods: The Surveillance Epidemiology and End Results-Medicare database was leveraged to design an observational, active-comparator new-user cohort study. U.S. men aged 66 and older who initiated either abiraterone or enzalutamide between 2011-2017 were identified, a period when both drugs were only approved for mCRPC (not castration-sensitive or non-metastatic prostate cancer). Propensity scores and inverse-probability-of-treatment weighting were used to balance measured confounders between the two exposure drugs, including demographics, tumor features, comorbidities, comedications, past cancer treatments, length of androgen deprivation therapy, and a claims-based frailty index. The primary outcomes were one-year and five-year overall survival and MACE. MACE was defined as a hospitalization for myocardial infarction, heart failure, or ischemic stroke or transient ischemic attack. Hazard ratios were obtained from a weighted Cox proportional hazards model (mortality) and a weighted Fine-and-Gray model (MACE).

Results: The study population consisted of 5,633 men 66 years of age and older diagnosed with mCRPC, of which 3,720 initiated abiraterone and 1,913 enzalutamide. The study population's median age at initiation was 77. Compared to enzalutamide initiators, the overall survival was similar amongst patients initiating abiraterone at both one-year (mortality hazard ratio (HR) = 1.05; 95% CI: 0.95– 1.17) and five-years of follow up (HR = 1.01; 95% CI: 0.95 – 1.08). The one-year risk of MACE was higher in abiraterone initiators (HR = 1.30; 95% CI: 1.01 – 1.67). The agents displayed similar effects on MACE when considering a five-year follow-up period (HR = 1.04; 95% CI: 0.88 - 1.23).

Conclusions: The long-term comparative effectiveness and cardiovascular safety of abiraterone and enzalutamide were similar, though a short-term increase in MACE was seen in abiraterone initiators, highlighting the importance of considering cardiovascular risk and cancer prognosis during therapy selection.