A Study to Understand About the Study Medicine Palbociclib in Breast Cancer Patients After it is Out in the Japanese Market

Study summary

The purpose of the study is to: * compare the chances of getting interstitial lung disease (ILD) in new users of palbociclib plus fulvestrant to new users of fulvestrant alone (using data from before palbociclib was out in the market) * look into the factors that can cause ILD in new users of palbociclib. This study uses patient data without giving out any personal information of the patient. This data is taken from a hospital-based claims database of the MDV database, that includes data from more than 400 hospitals in Japan. This study will use data of patients who are: * diagnosed with breast cancer that include newly treated with palbociclib and/or other endocrine-based therapies for inoperable or recurrent breast cancer between 25 November 2011 and 30 November 2024.

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Key things to know

Main goalNot specified

This describes the study’s primary purpose.

What is being studiedpalbociclib plus fulvestrant and fulvestrant

The study team can explain what participation involves.

Who it may be forEarly-stage or resectable · Recurrent or relapsed

These are broad labels—not an eligibility decision.

Checked against the public recordLast updated Jul 10, 2026 · Source: ClinicalTrials.gov

Is enrollment open?Completed

Ask the study team to confirm whether enrollment is open.

What kind of study?Not applicable

Observational

Where is it offered?1 U.S. location

Locations may change over time.

Who runs it?Pfizer

Study sponsor

Study overview

What this study is about

Purpose: Not specified
Study type: Observational
Phase: Not applicable
Sponsor: Pfizer
Interventions being studied: Drug: palbociclib plus fulvestrant; Drug: fulvestrant

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How this study is categorized

These labels come from structured fields and exact terms in the public record.

Disease setting

Early-stage or resectable→Recurrent or relapsed→

Public criteria

Who may be able to participate

The sponsor separates these requirements into two groups. You do not need to interpret them alone—use them to guide a conversation with the study team.

Requirements people may need to meetInclusion criteria

Having prescription records of drugs for endocrine therapy (aromatase inhibitors, SERDs, SERMs, and CDK4/6 inhibitors) from 25 November 2011 to 31 December 2024.
Having any breast cancer records with definitive diagnosis in the same month as the first prescription date.
Having any records in MDV database on or before 6 months prior to the first prescription date (\<= -180 days: first prescription date = 0 day).
Having any records in MDV database within 6 months prior to the first prescription date (-180 days to 0 day).

Reasons someone may not be able to joinExclusion criteria

Having any records of anti-HER2 medication (e.g., trastuzumab, pertuzumab, lapatinib or trastuzumab emtansine) from 25 November 2011 to 31 December 2024.
Having any records of second primary cancer with definitive diagnosis

Important: This is the sponsor’s public criteria, not a determination of eligibility. The study team must review your individual situation.

Study sites

U.S. locations

PfizerNew York, New York

Source and freshness
Processed from ClinicalTrials.gov. Last public update: Jul 10, 2026. Always confirm current availability with the study team.

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