(UroToday.com) The 2023 ESMO annual meeting included a session on prostate cancer, featuring a presentation by Dr. Daniel George discussing real-world overall survival with enzalutamide and abiraterone acetate in patients with chemotherapy-naïve metastatic castration-resistant prostate cancer (mCRPC). The US guidelines recommend both abiraterone and enzalutamide for patients with chemotherapy mCRPC. However, to date, there are no head-to-head phase 3 clinical trials comparing OS between enzalutamide and abiraterone. Accumulating data show shorter OS for abiraterone versus enzalutamide, and in the US, a detriment in OS with abiraterone versus enzalutamide has been observed in the VA health system and the Flatiron electronic medical records. Additionally, a French National Database (SNDS) study has previously reported improved real world OS outcomes with enzalutamide vs abiraterone.1 At the ESMO 2023 annual congress, Dr. George and colleagues compared OS in US Medicare patients with chemotherapy-naïve mCRPC who initiated enzalutamide or abiraterone.
This retrospective analysis of Medicare fee-for-service claims data (2009–2020) included adult men with ≥1 claim for prostate cancer and a metastatic diagnosis who were chemotherapy-naïve and initiated enzalutamide or abiraterone (index date) between September 10, 2014, and May 31, 2017. OS overall and by subgroups defined by baseline characteristics were evaluated using Kaplan–Meier analysis with inverse probability treatment weighting (IPTW) to adjust for potential baseline confounders.
Overall, 2,911 patients who initiated abiraterone and 2,595 patients who initiated enzalutamide were included in the study. Baseline characteristics were generally comparable between cohorts with several exceptions: higher baseline long-term corticosteroid use and lower proportion of diabetes in abiraterone treated patients compared to enzalutamide patients:
The median follow-up was 19.1 months for abiraterone and 20.3 months for enzalutamide. The IPTW-adjusted median OS was 20.6 months (95% CI 19.7, 21.4) for abiraterone and 22.5 months (95% CI 21.2, 23.8) for enzalutamide, with an IPTW-adjusted HR of 1.10 (95% CI 1.04, 1.16):
Median OS was significantly shorter for abiraterone vs enzalutamide in subgroups of patients who were ≥75 years old, white, low or middle/high socioeconomic status, and with baseline comorbidities (cardiovascular disease, diabetes, and renal disease):
Dr. George concluded his presentation by discussing real-world overall survival with enzalutamide and abiraterone acetate in patients with chemotherapy-naïve mCRPC with the following concluding statements:
- In a large, representative US Medicare dataset, patients with chemotherapy-naïve mCRPC treated with abiraterone had significantly shorter OS than those treated with enzalutamide
- These results validate previous real world studies and are robust across different healthcare systems [1]
- These findings may be particularly important in older patients and those with comorbidities
Presented by: Daniel J. George, MD, Duke Cancer Center, Durham, NC
Written by: Zachary Klaassen, MD, MSc – Urologic Oncologist, Associate Professor of Urology, Georgia Cancer Center, Wellstar MCG Health, @zklaassen_md on Twitter during the 2023 European Society of Medical Oncology (ESMO) Annual Meeting, Madrid, Spain, Fri, Oct 20 – Tues, Oct 24, 2023.
References:
- Scailteux LM, Campillo-Gimenez B, Kerbrat S, et al. Overall survival among chemotherapy-naïve patients with castration-resistant prostate cancer under abiraterone versus enzalutamide: A direct comparison based on a 2014-2018 French population study (the SPEAR cohort). Am J Epidemiol. 2021 Feb 1;190(3):413-422.