1827P - Real-world (RW) overall survival (OS) with enzalutamide (ENZ) and abiraterone acetate (ABI) in patients (pts) with chemotherapy (cx)-naïve metastatic castration-resistant prostate cancer (mCRPC)

Background

There are no head-to-head phase 3 clinical trials comparing OS between ENZ and ABI. A French National Database (SNDS) study reported improved RW OS with ENZ vs ABI.¹ We compared OS in US Medicare pts with cx-naïve mCRPC who initiated ENZ or ABI.

Methods

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 cx-naïve and initiated ENZ or ABI (index date) between September 10, 2014, and May 31, 2017. OS overall and by subgroups defined by baseline characteristics was evaluated using Kaplan–Meier analysis with inverse probability treatment weighting (IPTW) to adjust for potential baseline confounders.

Results

Overall, 2911 pts who initiated ABI and 2595 pts who initiated ENZ were included. Baseline characteristics were generally comparable between cohorts. Median follow-up was 19.1 months for ABI and 20.3 months for ENZ. The IPTW-adjusted median OS (95% CI) was 20.6 months (19.7, 21.4) for ABI and 22.5 months (21.2, 23.8) for ENZ, with an IPTW-adjusted hazard ratio (HR) of 1.10 (95% CI 1.04, 1.16; P<0.001). Median OS was significantly shorter for ABI vs ENZ in subgroups of pts who were ≥75 years old, White, low or middle/high (not shown) socioeconomic status (SES), and with baseline comorbidities (cardiovascular disease [CVD], diabetes, and renal disease; table). Table: 1827P

IPTW-adjusted OS

Conclusions

In the large, representative US Medicare dataset, pts with cx-naïve mCRPC treated with ABI had significantly shorter OS than those treated with ENZ. This study with >5500 pts validates previous RW studies reporting improved OS with ENZ vs ABI, including a prior French SNDS study with >10000 pts,¹ and shows that results are robust across different health systems. These findings may be particularly important in older pts and those with comorbidities. 1. Scailteux, et al. Am J Epidemiol. 2021;190:413–22.

Clinical trial identification

Editorial acknowledgement

Medical writing support funded by the sponsors was provided by Megan Christian of Onyx (a Prime Global agency).

Legal entity responsible for the study

Pfizer Inc. and Astellas Pharma Inc.

Funding

Pfizer Inc. and Astellas Pharma Inc.

Disclosure

D.J. George: Financial Interests, Institutional, Speaker, Consultant, Advisor: Bayer, Exelixis, Pfizer, Inc., Sanofi, Astellas Pharma, Inc., Innocrin Pharma, BMS, Genentech, Janssen, Merck Sharp & Dohme, Myovant Sciences, AstraZeneca, Michael J. Hennessy Associates, Constellation Pharmaceuticals, Physicians’ Education Resource, Propella Therapeutics, RevHealth, Xcures, Novartis, Dendreon, Acerta, Calithera Biosciences. K. Ramaswamy, J. Ivanova, B. Thompson, B. Emir: Financial Interests, Personal, Full or part-time Employment: Pfizer Inc.. H. Yang, Q. Liu, A. Zhang, A. Greatsinger: Financial Interests, Personal, Full or part-time Employment: Analysis Group, Inc.. A. Hong: Financial Interests, Personal, Full or part-time Employment: Pfizer Inc.; Financial Interests, Personal, Full or part-time Employment, Former employee: Astellas Pharma, Inc.. S.J. Freedland: Financial Interests, Institutional, Speaker, Consultant, Advisor: Astellas Pharma, Inc., AstraZeneca, Bayer, Clovis Oncology, Exact Sciences Corporation, Janssen Biotech, Merck, Myovant Sciences, Pfizer Inc., Sanofi, Tempus.