Study to Evaluate Overall Survival in Japanese Patients With HR+/HER2- Advanced Breast Cancer Treated With Palbociclib Plus Letrozole

November 22, 2025 updated by: Pfizer

Retrospective, Multicenter, Observational Study to Evaluate Overall Survival in Japanese Patients With HR+/HER2- Advanced Breast Cancer Treated With Palbociclib Plus Letrozole

This is a retrospective, multicenter, observational study in Japan. The primary objective is to evaluate overall survival (OS) in Japanese patients with HR+/HER2- advanced breast cancer who have been treated with palbociclib plus letrozole. This observational study was planned as follow-up study of Japanese phase 2 study of palbociclib (NCT01684215, phase 2 portion of A5481010 study).

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Completed

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Observational

Enrollment (Actual)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
42

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

  • Japan
      • Fukuoka, Japan, 811-1395
        • National Hospital Organization Kyushu Cancer Center
      • Kagoshima, Japan, 892-0833
        • Hakuaikai Medical Corporation Sagara Hospital
      • Kumamoto, Japan, 862-8655
        • Kumamoto Shinto General Hospital
      • Kyoto, Japan, 606-8507
        • Kyoto University Hospital
      • Nagoya, Japan, 464-8681
        • Aichi Cancer Center
      • Osaka, Japan, 540-0006
        • National Hospital Organization - Osaka National Hospital - Institute For Clinical Research
    • Chiba
      • Chiba, Chiba, Japan, 260-8717
        • Chiba Cancer Center
    • Ehime
      • Matsuyama, Ehime, Japan, 791-0280
        • National Hospital Organization Shikoku Cancer Center
    • Hiroshima
      • Hiroshima, Hiroshima, Japan, 730-8518
        • Hiroshima City Hiroshima Citizens Hospital
    • Hokkaido
      • Sapporo, Hokkaido, Japan, 003-0804
        • National Hospital Organization Hokkaido Cancer Center
    • Kumamoto
      • Kumamoto, Kumamoto, Japan, 860-8556
        • Kumamoto University Hospital
    • Saitama
      • Kita-adachi-gun, Saitama, Japan, 362-0806
        • Saitama Cancer Center
    • Tokyo
      • Chuo-ku, Tokyo, Japan, 104-0045
        • National Cancer Center Hospital

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

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

20 years and older (Adult, Older Adult)

Accepts Healthy Volunteers

No

Sampling Method

Non-Probability Sample

Study Population

Patients who participated, treated with palbociclib plus letrozole, and under follow-up for survival in J-Ph2

Description

Inclusion Criteria:

  1. Participated, treated with palbociclib plus letrozole in J-Ph2, and was under follow-up for survival at the study completion of J-Ph2.
  2. For patients who are still alive and have routine visits to the study site, evidence of a personally signed and dated informed consent document indicating that the patient has been informed of all pertinent aspects of the study. For patients who are still alive and had been transferred to another hospital, evidence that the patient has been informed of all pertinent aspects of the study and oral or written informed consent is obtained. For patients who had already passed away, the conduct of this study will be disclosed, and the patients' legally acceptable representatives will be guaranteed an opportunity to refuse data collection for the patients in accordance with the Ethical Guidelines for Medical and Health Research Involving Human Subjects

Exclusion Criteria:

1. There are no exclusion criteria for this study.

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

  • Observational Models: Cohort
  • Time Perspectives: Retrospective

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Measure Description
Time Frame
Overall Survival (OS)
Time Frame: From the date of the first dose of the treatment in study A5481010 to the date of any-cause death or censoring date (maximum of 103.16 months of follow-up); data collected and observed retrospectively over 32 months in A5481154 study
OS was defined as the time from the date of the first dose of the investigational product in Japanese Phase 2 study (A5481010) to the date of any-cause death. In the absence of confirmation of death, survival time was censored to last date the participant was known to be alive. Kaplan-Meier method was used for analysis.
From the date of the first dose of the treatment in study A5481010 to the date of any-cause death or censoring date (maximum of 103.16 months of follow-up); data collected and observed retrospectively over 32 months in A5481154 study

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
Percentage of Participants According to Types and Line of Subsequent Treatment
Time Frame: From start of subsequent treatment in study A5481010 until date of death, withdrawal of consent or end of study (maximum of 103.16 months of follow-up); data collected and observed retrospectively over 32 months in A5481154 study
Participants were classified based on types of subsequent treatment and by line of subsequent treatment. Subsequent treatments included: endocrine therapy-based, chemotherapy-based and others (Investigational drug + Endocrine therapy/Chemotherapy).
From start of subsequent treatment in study A5481010 until date of death, withdrawal of consent or end of study (maximum of 103.16 months of follow-up); data collected and observed retrospectively over 32 months in A5481154 study
Duration of Subsequent Therapy by Line of Therapy
Time Frame: From start of subsequent treatment in study A5481010 until date of death, withdrawal of consent or end of study (maximum of 103.16 months of follow-up); data collected and observed retrospectively over 32 months in A5481154 study
Duration of subsequent therapy defined as time from the start date to the end date of each line of treatment among participants who received subsequent treatment. Kaplan-Meier method was used.
From start of subsequent treatment in study A5481010 until date of death, withdrawal of consent or end of study (maximum of 103.16 months of follow-up); data collected and observed retrospectively over 32 months in A5481154 study

Collaborators and Investigators

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

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
Pfizer

Investigators

Investigators

A researcher involved in a clinical study. Related terms include site principal investigator, site sub-investigator, study chair, study director, and study principal investigator.
  • 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.

General Publications

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)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
February 3, 2021

Primary Completion (Actual)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
September 29, 2023

Study Completion (Actual)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
September 29, 2023

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
January 28, 2021

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
January 28, 2021

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
February 3, 2021

Study Record Updates

Last Update Posted (Estimated)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
December 9, 2025

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
November 22, 2025

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
November 1, 2025

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • A5481154
  • NCT04735367 (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.

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

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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