Real-world Outcomes of Patients With HER2+ Metastatic Breast Cancer After Treatment With Trastuzumab Deruxtecan

Real-world Outcomes of Patients With HER2-positive (HER2+) Metastatic Breast Cancer (mBC) After Treatment With Trastuzumab Deruxtecan (T-DXd) in the United States

This study will explore treatment patterns and clinical outcomes using the US-based Flatiron Health database to describe patients with HER2+ mBC who were previously treated with T-DXd to better characterize this population and inform internal decision making in this rapidly changing therapeutic landscape.

Study Overview

• Status: Completed
• Conditions: HER2-positive Breast Cancer
• Intervention / Treatment: Other: No drug

Detailed Description

This study will utilize a longitudinal, demographically and geographically diverse database derived from Electronic Health Record data. No study medication will be supplied or administered for this protocol. The primary research objective is to describe the real-world progression-free survival (rwPFS) in HER2+ mBC patients who initiated a subsequent line of therapy (LOT) after a T-DXd-containing LOT in the metastatic setting.

Secondary research objectives include describing the real-world overall survival (rwOS), patient demographics and clinical characteristics, real-world time to next treatment (rwTTNT), and real-world time to treatment discontinuation (rwTTD) in HER2+ mBC patients who initiated a subsequent LOT after a T-DXd-containing LOT in the metastatic setting. Treatment patterns and sequencing in HER2+ mBC patients for subsequent LOTs following initial treatment with T-DXd will also be assessed.

• Study Type: Observational
• Enrollment (Actual): 228

Contacts and Locations

Study Locations

• United States
  • New York
    • New York, New York, United States, 10013
      • Flatiron Health, Inc

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

• Sampling Method: Non-Probability Sample

Study Population

The study population will consist of adults in the Flatiron mBC EDM who were diagnosed with HER2+ mBC during the study period and initiated a subsequent LOT after the initial T-DXd-containing LOT in the metastatic setting.

Description

Inclusion Criteria

Patients must meet all the inclusion criteria below to be included in the study population:

1. Patients with evidence of stage IV or recurrent mBC with a metastatic diagnosis date on or after January 1, 2011.
2. Patients aged ≥18 years old at mBC diagnosis date.
3. Patients with ≥1 T-DXd-containing LOT in the metastatic setting.
4. Patients with evidence of a subsequent LOT following the first T-DXd-containing LOT in the metastatic setting. The LOT subsequent to the first T-DXd-containing LOT in the metastatic setting will be the index LOT. Index date will be the index LOT start date.
5. Patients whose closest HER2 test result (defined as immunohistochemistry [IHC] 3+ or in situ hybridization [ISH]+) recorded prior to or on the index date was a HER2+ test result.
6. Patients with index date occurring at least 90 days prior to end of study period (March 31st, 2024).

Exclusion Criteria No exclusion criteria will be imposed.

Study Plan

How is the study designed?

Number of groups / cohorts

1

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
HER2-positive breast cancer; Patients diagnosed with HER2-positive metastatic breast cancer who initiated a subsequent LOT after the initial T-DXd-containing LOT in the metastatic setting.	Other: No drug; This is an non-interventional, observational study. No drug will be provided or administered as part of this protocol.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Real-world Progression-free Survival (rwPFS)	rwPFS is defined as the interval in months between the index date until the first evidence of progression or death as documented by Flatiron.	Index date (index LOT start date) to date of earliest disease progression >14 days after the index date or date of death, whichever occurs first, up to approximately 13 years 3 months

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Real-world Time to Next Treatment (rwTTNT)	rwTTNT is defined as the time in months between index date and initiation of next LOT, or death, whichever occurs first.	Index date (index LOT start date) to next LOT start date or, in the absence of next LOT, death, whichever occurs first, up to approximately 13 years 3 months
Real-world Time to Treatment Discontinuation (rwTTD)	rwTTD is defined as the time in months between index date and date of treatment discontinuation or death, whichever occurs first.	Index date (index LOT start date) to date treatment is discontinued, up to approximately 13 years 3 months
Treatment Patterns by Type of Line of Therapy	Treatment patterns will be described by LOT (monotherapy, combination therapy, and treatment sequence).	Index date (index LOT start date) to end of study period, up to approximately 13 years 3 months

Collaborators and Investigators

• Sponsor: Daiichi Sankyo
• Investigators: Study Director: Project Manager, Daiichi Sankyo

Study record dates

Study Major Dates

• Study Start (Actual): January 20, 2025
• Primary Completion (Actual): June 16, 2025
• Study Completion (Actual): June 16, 2025

Study Registration Dates

• First Submitted: February 12, 2025
• First Submitted That Met QC Criteria: February 12, 2025
• First Posted (Actual): February 18, 2025

Study Record Updates

• Last Update Posted (Estimated): July 8, 2025
• Last Update Submitted That Met QC Criteria: July 7, 2025
• Last Verified: July 1, 2025

More Information

Terms related to this study

• Keywords: HER2-positive breast cancer; Real-world outcomes
• Additional Relevant MeSH Terms: Neoplasms by Site; Neoplasms; Skin Diseases; Breast Diseases; Breast Neoplasms
• Other Study ID Numbers: U31402-0010-NIS-MA

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No