Skeletal-related events after abiraterone or enzalutamide in patients with metastatic castration-resistant prostate cancer: A population-based study using the SEER-Medicare linked dataset.

Skeletal-related events (SREs) from bone metastases disease carry significant morbidity in men with metastatic castration resistant prostate cancer (mCRPC). The differential risk of SREs among patients receiving abiraterone acetate (AA) or enzalutamide (ENZ) is unknown.

To compare the risk of SREs among men with mCRPC receiving AA or ENZ, a retrospective cohort study using the SEER-Medicare Linked Database was conducted. Men with prostate cancer aged ≥65 years at first AA or ENZ prescription (index date) from 2011 to 2015 were identified. Patients were followed until the earliest occurrence of SRE, death, Medicare disenrollment, or December 31, 2016. The primary outcome was a composite endpoint of SRE (pathologic fracture, spinal cord compression, or surgery or radiation to bone) after the index date. Multivariable logistic regressions including key demographic and clinical covariates with death as a competing risk were conducted.

Overall, 5,856 patients were identified (4,207 received AA and 1,649 received ENZ). Median age was 76.5 years (IQR 71.4-82.3), 4,557 (77.8%) were White, 1,112 (19.2%) had recent chemotherapy, and 2,730 (46.6%) had recent zoledronic acid or denosumab. Eight-hundred and thirty-seven (14.3%) patients had ≥1 SRE after index date. In multivariable analyses, there was no difference in SRE risk based on AA and ENZ (HR=0.99 for ENZ, 95%CI 0.84-1.16, P=0.890). Denosumab was associated with lower SRE risk (HR=0.75, 95%CI 0.64-0.88, P=0.001).

In this large cohort of men with mCRPC, there was no difference in risk of SRE between AA and ENZ. Decision-making should be informed by prior therapies, comorbidities, toxicity profiles, and patient preferences. Denosumab has evidence of benefit in preventing SREs in this real-world population.

Urologic oncology. 2022 Jun 21 [Epub ahead of print]

Daniel H Kwon, Alan Paciorek, Li Zhang, Hala T Borno, Matthew Bucknor, Eric J Small, Rahul R Aggarwal

Department of Medicine, University of California, San Francisco, CA. Electronic address: ., Department of Epidemiology and Biostatistics, University of California, San Francisco, CA., Department of Epidemiology and Biostatistics, University of California, San Francisco, CA; Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, CA., Department of Medicine, University of California, San Francisco, CA; Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, CA., Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA.

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