A Study to Learn About the Study Medicines Called Enzalutamide and Abiraterone in People With Metastatic Castration-resistant Prostate Cancer

February 6, 2026 updated by: Pfizer

A Real-World Comparison of Clinical Outcomes in Chemotherapy-naive Metastatic Castration-resistant Prostate Cancer (mCRPC) Patients Who Initiated Enzalutamide vs. Abiraterone Acetate (Abiraterone) in Flatiron Electronic Health Record (EHR) Database

The purpose of this real-world study is to learn about the effects of 2 study medicines called enzalutamide and abiraterone used to treat metastatic castration-resistant prostate cancer (mCRPC).

Prostate cancer is one of the most common cancers in men. The prostate is a gland in the male body that helps make semen. Most prostate cancers need male sex hormones, such as testosterone, to grow. Prostate cancer that keeps growing even when the amount of testosterone in the body is reduced to very low levels is known as "castration-resistant". Metastatic cancer is a cancer that has spread to other parts of the body.

This is a real-world study, not a clinical trial. This means that researchers will look at what happens when men receive the treatments prescribed by their own doctor as part of their usual healthcare treatment. In this study, researchers will use information from the Flatiron Electronic Health Record (EHR) database.

The study will include patients' information from the database for men who:

  • Were confirmed by medical tests to have mCRPC
  • Started first-line treatment with enzalutamide or abiraterone (index date) for mCRPC
  • Had not received chemotherapy treatment before index date
  • Were 18 years of age or older on index date

Men who are part of this study will receive enzalutamide or abiraterone as part of their usual treatment for mCRPC.

We will compare the following between men receiving enzalutamide and men receiving abiraterone:

  • time from treatment start until death,
  • treatment duration, and
  • time to next treatment. This study will use patient information from the database until the end of information that is available.

Study Overview

Status

Completed

Conditions

Intervention / Treatment

Study Type

Observational

Enrollment (Actual)

2731

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • United States
    • New York
      • New York, New York, United States, 10001
        • Pfizer Inc

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Sampling Method

Non-Probability Sample

Study Population

Men with chemotherapy-naïve mCRPC (aged ≥18 years) who initiated enzalutamide or abiraterone and met eligibility criteria will be included in the study. Patients will be identified from the Flatiron EHR database.

Description

Inclusion Criteria:

  • Male with metastatic prostate cancer diagnosis and abstracted castration-resistant prostate cancer diagnosis
  • Initiated enzalutamide or abiraterone within 14 days prior to or after the metastatic castration-resistant prostate cancer diagnosis. The initiation date of enzalutamide or abiraterone will be defined as the index date.
  • At least 18 years old at the index date

Exclusion Criteria:

  • Received chemotherapy, novel hormonal therapy, radium-223, olaparib/rucaparib, or immunotherapy prior to the index date
  • Had a prior history of other cancers

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

Cohorts and Interventions

Group / Cohort
Intervention / Treatment
Enzalutamide cohort
Patients with mCRPC initiating enzalutamide
Drug: Enzalutamide
As provided in real-world setting
Other Names:
  • Xtandi
Abiraterone cohort
Patients with mCRPC initiating abiraterone acetate
Drug: Abiraterone acetate
As provided in real-world setting
Other Names:
  • Yonsa, Zytiga

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Overall Survival (OS): Adjusted Using Inverse Probability Treatment Weighting (IPTW)
Time Frame: From index date to date of death or censoring date, whichever occurred first (approximately 104.7 months); retrospective data retrieved and evaluated during approximately 18.7 months
OS was defined as the time from the initiation of enzalutamide or abiraterone (i.e., index date) to the date of death. Participants who did not die during this period were censored at their last available follow-up, which was defined as the earlier of end of data availability or last participant contact. Index date was defined as the date of initiation of enzalutamide or abiraterone and their index date was required to occur during the index period. Kaplan-Meier (weighted) method was used for analysis.
From index date to date of death or censoring date, whichever occurred first (approximately 104.7 months); retrospective data retrieved and evaluated during approximately 18.7 months

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
OS Without Subsequent Therapy: Adjusted Using IPTW
Time Frame: From index date to date of death or censoring date, whichever occurred first (approximately 104.7 months); retrospective data retrieved and evaluated during approximately 18.7 months
OS was defined as the time from the initiation of enzalutamide or abiraterone (i.e., index date) to the date of death. Participants who did not die during this period were censored at their last available follow-up, which was defined as the earlier of end of data availability or last participant contact. Index date was defined as the date of initiation of enzalutamide or abiraterone and their index date was required to occur during the index period. OS of only those participants who initiated abiraterone and enzalutamide on the index date and did not receive subsequent systemic anti-neoplastic therapy were reported in this outcome measure. Kaplan-Meier (weighted) method was used for analysis.
From index date to date of death or censoring date, whichever occurred first (approximately 104.7 months); retrospective data retrieved and evaluated during approximately 18.7 months
Time to Treatment Discontinuation (TTD): Adjusted Using IPTW
Time Frame: From index date to date of treatment discontinuation or censoring date, whichever occurred first (approximately 104.7 months); retrospective data retrieved and evaluated during approximately 18.7 months
Treatment duration of the index treatment was defined as the time from the initiation of enzalutamide or abiraterone (i.e., index date) to the discontinuation date. Index date was defined as the date of initiation of enzalutamide or abiraterone and their index date was required to occur during the index period. Discontinuation was defined as the earliest of 1) death, 2) abstracted end date for last enzalutamide or abiraterone drug episode that started within the index treatment line of therapy (LOT) (drug episodes for abstracted oral therapies from the Flatiron Drug Episode table), or 3) day before the start of next LOT. Participants who did not discontinue were censored at their last available follow-up, which was defined as the earlier of end of data availability or last participant contact. Kaplan-Meier (weighted) method was used for analysis.
From index date to date of treatment discontinuation or censoring date, whichever occurred first (approximately 104.7 months); retrospective data retrieved and evaluated during approximately 18.7 months
Time to Subsequent Therapy (TTST): Adjusted Using IPTW
Time Frame: From index date to date of start of next LOT or censoring date, whichever occurred first (approximately 104.7 months); retrospective data retrieved and evaluated during approximately 18.7 months
TTST was defined as the time from the initiation of enzalutamide or abiraterone (i.e., index date) to the start of next LOT. Index date was defined as the date of initiation of enzalutamide or abiraterone and their index date was required to occur during the index period. Participants who did not start a new LOT were censored at their last available follow-up, which was defined as the earliest of 1) death, 2) end of data availability or 3) last participant contact. Kaplan-Meier (weighted) method was used for analysis.
From index date to date of start of next LOT or censoring date, whichever occurred first (approximately 104.7 months); retrospective data retrieved and evaluated during approximately 18.7 months

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Pfizer

Collaborators

Astellas Pharma Inc

Investigators

  • Study Director: Pfizer CT.gov Call Center, Pfizer

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

Helpful Links

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

July 24, 2023

Primary Completion (Actual)

February 14, 2025

Study Completion (Actual)

February 14, 2025

Study Registration Dates

First Submitted

July 21, 2023

First Submitted That Met QC Criteria

July 21, 2023

First Posted (Actual)

August 1, 2023

Study Record Updates

Last Update Posted (Actual)

February 25, 2026

Last Update Submitted That Met QC Criteria

February 6, 2026

Last Verified

February 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • C3431047
  • NCT05968599 (Registry Identifier: ClinicalTrials.gov)

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

IPD Plan Description

Pfizer will provide access to individual de-identified participant data and related study documents (e.g. protocol, Statistical Analysis Plan (SAP), Clinical Study Report (CSR)) upon request from qualified researchers, and subject to certain criteria, conditions, and exceptions. Further details on Pfizer's data sharing criteria and process for requesting access can be found at: https://www.pfizer.com/science/clinical_trials/trial_data_and_results/data_requests.

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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