AUA 2019: Survival Rates and Economic Outcomes in Chemotherapy-Naïve Metastatic Castrate Resistant Prostate Cancer Patients treated with Abiraterone Acetate or Enzalutamide

Chicago, IL (UroToday.com) Prostate cancer is the second leading cause of cancer death among US males and accounts for a great proportion of health expenditures – this expenditure, just for prostate cancer alone, is estimated to be $15-16 billion by 2020. Indeed, many of these costs are directly attributed to systemic therapy used in the advanced prostate cancer disease state. During the advanced prostate cancer podium session at AUA 2019, Dr. Daniel George and colleagues presented real world results of the economics associated with patients receiving enzalutamide or abiraterone for metastatic castration-resistant prostate cancer (mCRPC). Few real-world studies have evaluated the comparative effectiveness of abiraterone and enzalutamide on overall survival (OS) and none have described the economic burden associated with US military veterans receiving either treatment. As such, the objective of their study was to evaluate OS and economic outcomes among chemotherapy-naive mCRPC patients treated with either of these medications.

This study was a retrospective analysis of 3,174 male patients among those in the Veterans Health Administration (VHA) database. The study selection flow chart is as follows:

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Between April 1, 2013 and March 31, 2018, mCRPC patients with evidence of surgical or medical castration, a pharmacy claim for abiraterone acetate or enzalutamide (1st claim date = index date) following surgical or medical castration, and with no chemotherapy treatment during the 12 months pre-index date were identified. Patients had to have continuous VHA enrollment for more 12 months pre- and post-index date and were followed until death or disenrollment from the VA system. The authors used Kaplan-Meier analysis to estimate OS and Cox proportional hazards regression models were used to examine the impact of treatment on survival. Subsequently, patients initiating abiraterone acetate were 1:1 propensity score matched with those starting enzalutamide. All-cause and prostate cancer-related resource use and costs per-patient-per-month (PPPM) were compared between the matched cohorts during the 12 months post-index date.

There were 1,945 abiraterone acetate and 1,229 enzalutamide mCRPC patients with mean ages of 73 and 74 years of age, respectively. Patients initiating enzalutamide had a significantly longer OS compared to those starting abiraterone acetate (29.3 months vs 26.0 months; HR 0.87, 95%CI 0.78-0.96):

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After propensity score matching, there were 1,160 patients in each cohort. Compared to abiraterone acetate patients, enzalutamide patients had fewer mean all-cause outpatient visits PPPM (2.51 vs 2.86; p < 0.0001) and fewer mean prostate cancer-related outpatient visits PPPM (0.86 vs 1.03; p < 0.0001). Enzalutamide patients also had lower:

Mean all-cause outpatient costs PPPM ($2,588 vs $3,115; p < 0.0001)
Mean total costs PPPM ($8,085 vs $9,092; p = 0.0002)
Prostate cancer-related outpatient costs PPPM ($1,356 vs $1,775; p < 0.0001)
Mean total costs PPPM ($6,321 vs $7,280; p < 0.0001)

Dr. George concluded his presentation with several summary points:

In this real-world analysis, patients prescribed enzalutamide compared to abiraterone acetate had great median overall survival, reduced risk of death, fewer prostate cancer outpatient visits and shorter inpatient length of stay, as well as lower all-cause and prostate cancer-related health care costs
As a limitation, Dr. George notes that this study was restricted by the factors available in the claims data and that other factors not included in the analysis may affect survival

Presented by: Daniel George, MD, Professor of Medicine and Surgery, Divisions of Medical Oncology and Urology in the Duke University School of Medicine and leads the Duke Prostate and Urologic Cancer Center, Durham, North Carolina
Co-Authors: Krishnan Ramaswamy, New York, NY, Stanislav Lechpammer, San Francisco, CA, Jack Mardekian, New York, NY, Neil M. Schultz, Northbrook, IL, Ahong Huang, Li Wang, Plano, TX, Onur Baser, Ann Arbor, MI

Written by: Zachary Klaassen, MD, MSc – Assistant Professor of Urology, Georgia Cancer Center, Augusta University - Medical College of Georgia, Twitter:@zklaassen_md at the American Urological Association's 2019 Annual Meeting (AUA 2019), May 3 – 6, 2019 in Chicago, Illinois

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