Trial Outcomes & Findings for A Study to Learn About the Study Medicines Called Enzalutamide and Abiraterone in People With Metastatic Castration-resistant Prostate Cancer (NCT NCT05968599)

Results Overview

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.

Recruitment status

COMPLETED

Target enrollment

2731 participants

Primary outcome timeframe

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

Results posted on

2026-02-25

Participant Flow

Data of eligible participants with metastatic castration-resistant prostate cancer (mCRPC), who initiated abiraterone or enzalutamide from 10-Sep-2014 to 30-Jun-2020 (approximately 69.7 months = index period) were retrieved from Flatiron electronic health record (EHR) database from 10-Sep-2014 to 31-May-2023 (approximately 104.7 months = data collection period).

Retrospective data were retrieved and evaluated per objectives of this observational study from 24-Jul-2023 to 14-Feb-2025 (approximately 18.7 months).

Participant milestones

Participant milestones
Measure	Abiraterone Participants diagnosed with mCRPC who initiated abiraterone, in real-world setting under routine clinical practice were included. Data from these participants were observed retrospectively. No intervention was administered during this study.	Enzalutamide Participants diagnosed with mCRPC who initiated enzalutamide, in real-world setting under routine clinical practice were included. Data from these participants were observed retrospectively. No intervention was administered during this study.
Overall Study STARTED	1316	1415
Overall Study COMPLETED	1316	1415
Overall Study NOT COMPLETED	0	0

Reasons for withdrawal

Withdrawal data not reported

Baseline Characteristics

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

Baseline characteristics by cohort

Baseline characteristics by cohort
Measure	Abiraterone n=1316 Participants Participants diagnosed with mCRPC who initiated abiraterone, in real-world setting under routine clinical practice were included. Data from these participants were observed retrospectively. No intervention was administered during this study.	Enzalutamide n=1415 Participants Participants diagnosed with mCRPC who initiated enzalutamide, in real-world setting under routine clinical practice were included. Data from these participants were observed retrospectively. No intervention was administered during this study.	Total n=2731 Participants Total of all reporting groups
Age, Continuous	74.5 Years STANDARD_DEVIATION 8.1 • n=24 Participants	75.3 Years STANDARD_DEVIATION 8.0 • n=20 Participants	74.9 Years STANDARD_DEVIATION 8 • n=40 Participants
Sex: Female, Male Female	0 Participants n=24 Participants	0 Participants n=20 Participants	0 Participants n=40 Participants
Sex: Female, Male Male	1316 Participants n=24 Participants	1415 Participants n=20 Participants	2731 Participants n=40 Participants
Race/Ethnicity, Customized White	796 Participants n=24 Participants	908 Participants n=20 Participants	1704 Participants n=40 Participants
Race/Ethnicity, Customized Black	140 Participants n=24 Participants	137 Participants n=20 Participants	277 Participants n=40 Participants
Race/Ethnicity, Customized Hispanic or Latino	81 Participants n=24 Participants	74 Participants n=20 Participants	155 Participants n=40 Participants
Race/Ethnicity, Customized Asian	22 Participants n=24 Participants	23 Participants n=20 Participants	45 Participants n=40 Participants
Race/Ethnicity, Customized Other race	189 Participants n=24 Participants	183 Participants n=20 Participants	372 Participants n=40 Participants
Race/Ethnicity, Customized Unknown	88 Participants n=24 Participants	90 Participants n=20 Participants	178 Participants n=40 Participants

PRIMARY outcome

Timeframe: 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

Population: Analysis population included all participants included in this study, and were adjusted for baseline confounders (demographics, clinical characteristics, prior treatments, comorbidities) using IPTW method. As numbers were adjusted using IPTW, pseudo set was derived. Hence, numbers reported against "Overall Number of Participants Analyzed" (N) for both the arms differ from the unadjusted (raw) numbers presented in participant flow and baseline characteristics section.

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.

Outcome measures

Outcome measures
Measure	Abiraterone n=1382 Participants Participants diagnosed with mCRPC who initiated abiraterone, in real-world setting under routine clinical practice were included. Data from these participants were observed retrospectively. No intervention was administered during this study.	Enzalutamide n=1257 Participants Participants diagnosed with mCRPC who initiated enzalutamide, in real-world setting under routine clinical practice were included. Data from these participants were observed retrospectively. No intervention was administered during this study.
Overall Survival (OS): Adjusted Using Inverse Probability Treatment Weighting (IPTW)	24.63 Months Interval 22.93 to 26.33	25.77 Months Interval 24.3 to 27.6

SECONDARY outcome

Timeframe: 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

Population: Analysis population included a sub-set of participants included in this study, who did not receive subsequent systemic anti-neoplastic therapy. The evaluable number of participants for this outcome were adjusted for baseline confounders (demographics, clinical characteristics, prior treatments, comorbidities) using IPTW method. As numbers were adjusted using IPTW, pseudo sub-set was derived. Here, 'N' signifies participants evaluable for this outcome measure after applying ITPW.

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.

Outcome measures

Outcome measures
Measure	Abiraterone n=563 Participants Participants diagnosed with mCRPC who initiated abiraterone, in real-world setting under routine clinical practice were included. Data from these participants were observed retrospectively. No intervention was administered during this study.	Enzalutamide n=473 Participants Participants diagnosed with mCRPC who initiated enzalutamide, in real-world setting under routine clinical practice were included. Data from these participants were observed retrospectively. No intervention was administered during this study.
OS Without Subsequent Therapy: Adjusted Using IPTW	14.03 Months Interval 12.37 to 15.63	17.73 Months Interval 14.87 to 20.83

SECONDARY outcome

Timeframe: 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

Population: Analysis population included all participants included in this study, and were adjusted for baseline confounders (demographics, clinical characteristics, prior treatments, comorbidities) using IPTW method. As numbers were adjusted using IPTW, pseudo set was derived. Hence, numbers reported against "Overall Number of Participants Analyzed" for both the arms differ from the unadjusted (raw) numbers presented in participant flow and baseline characteristics section.

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.

Outcome measures

Outcome measures
Measure	Abiraterone n=1382 Participants Participants diagnosed with mCRPC who initiated abiraterone, in real-world setting under routine clinical practice were included. Data from these participants were observed retrospectively. No intervention was administered during this study.	Enzalutamide n=1257 Participants Participants diagnosed with mCRPC who initiated enzalutamide, in real-world setting under routine clinical practice were included. Data from these participants were observed retrospectively. No intervention was administered during this study.
Time to Treatment Discontinuation (TTD): Adjusted Using IPTW	7.87 Months Interval 7.1 to 8.5	9.50 Months Interval 8.67 to 10.13

SECONDARY outcome

Timeframe: 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

Population: Analysis population included all participants included in this study, and were adjusted for baseline confounders (demographics, clinical characteristics, prior treatments, comorbidities) using IPTW method. As numbers were adjusted using IPTW, pseudo set was derived. Hence, numbers reported against "Overall Number of Participants Analyzed" for both the arms differ from the unadjusted (raw) numbers presented in participant flow and baseline characteristics section.

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.

Outcome measures

Outcome measures
Measure	Abiraterone n=1382 Participants Participants diagnosed with mCRPC who initiated abiraterone, in real-world setting under routine clinical practice were included. Data from these participants were observed retrospectively. No intervention was administered during this study.	Enzalutamide n=1257 Participants Participants diagnosed with mCRPC who initiated enzalutamide, in real-world setting under routine clinical practice were included. Data from these participants were observed retrospectively. No intervention was administered during this study.
Time to Subsequent Therapy (TTST): Adjusted Using IPTW	14.70 Months Interval 13.47 to 16.27	17.90 Months Interval 16.4 to 19.8

Adverse Events

Abiraterone

Serious events: 0 serious events

Other events: 0 other events

Deaths: 1007 deaths

Enzalutamide

Serious events: 0 serious events

Other events: 0 other events

Deaths: 1036 deaths

Serious adverse events

Adverse event data not reported

Other adverse events

Adverse event data not reported

Additional Information

Pfizer ClinicalTrials.gov Call Center

Pfizer Inc.

Phone: 1-800-718-1021

Email: [email protected]

Results disclosure agreements

Principal investigator is a sponsor employee Pfizer has the right to review disclosures, requesting a delay of less than 60 days. Investigator will postpone single center publications until after disclosure of pooled data (all sites), less than 12 months from study completion/termination at all participating sites. Investigator may not disclose previously undisclosed confidential information other than study results.
Publication restrictions are in place

Restriction type: OTHER