Trastuzumab Emtansine(T-DM1) After Trastuzumab Deruxtecan(T-DXd) in HER2-Positive Breast Cancer in Korea

Prospective Observational Study of Trastuzumab Emtansine Immediately After Trastuzumab Deruxtecan in Patients With Advanced Human Epidermal Growth Factor Receptor 2-Positive Breast Cancer in Korea

Prospective observational study of trastuzumab emtansine immediately after trastuzumab deruxtecan in patients with advanced HER2-positive breast cancer in Korea

Study Overview

• Status: Recruiting
• Conditions: Cancer of Breast; Trastuzumab Emtansine; Trastuzumab Deruxtecan

• Study Type: Observational
• Enrollment (Estimated): 100

Contacts and Locations

• Study Contact: Name: Kyung-Hun Lee, MD, PhD; Phone Number: 82-2-2072-7207; Email: kyunghunlee@snu.ac.kr

Study Locations

• South Korea
  • Seoul, South Korea, 03080
    • Recruiting
    • Seoul National University Hospital
    • Contact: Kyung-Hun Lee, MD, PhD; Phone Number: 82-2-2072-7207; Email: kyunghunlee@snu.ac.kr

Participation Criteria

Eligibility Criteria

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

• Sampling Method: Probability Sample

Study Population

• Signed Informed Consent Form, when the patient is alive and not lost to follow- up.
• Age ≥ 19 years old.
• Histologically or cytologically confirmed, HER2-positive advanced breast cancer which is either locally advanced precluding resection or metastatic.
• Prior treatment with T-Dxd in the advanced setting
• Intention to treat with T-DM1 as next therapy upon progression from T-Dxd

Patients who meet any of the following criteria will be excluded from study entry:

• Any systemic treatment, other than T-DM1, for breast cancer after T-Dxd (With an exception, endocrine agents not in combination with cytotoxics or antibody-drug conjugates will be permitted in the study)
• Has been previously treated with T-DM1 for advanced breast cancer
• Has been previously treated with 4 or more lines of therapy for advanced breast cancer

Description

Inclusion Criteria:

• HER2-positive, advanced (unresectable locally advanced or metastatic) breast cancer
• Prior treatment with trastuzumab deruxtecan(T-DXd) in the advanced setting
• Intention to treat with Trastuzumab Emtansine (T-DM1) as first therapy upon T-DXd progression

Exclusion Criteria:

• Any systemic treatment, other than T-DM1, for breast cancer after trastuzumab deruxtecan (As an exception, patients treated with endocrine agents, not in combination with cytotoxics or antibody-drug conjugates, will be permitted in the study)
• Has been previously treated with T-DM1 for advanced breast cancer

• Has been previously treated with 4 or more lines of therapy for advanced breast cancer

  • Half (50%) or more patients will be those who were treated with second-line trastuzumab deruxtecan (i.e. patients at the later line will be capped).

Study Plan

How is the study designed?

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
progression-free survival (PFS)	PFS will be assessed by physicians as per routine clinical practice. CT and/or MRI scans will be at baseline and every 2-4 cycles at the treating physician's discretion, reflecting the observational study design.	PFS is defined as the time from treatment initiation to the first occurrence of disease progression or death from any cause, whichever occurs first, assessed up to 12 months.

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
objective response rate (ORR)	• objective response rate (ORR)	12-month
12-month survival rate	12-month survival rate	12-month
time-to-discontinuation (TTD)	time-to-discontinuation (TTD)	12-month
time-to-next-line-treatment (TTNT)	time-to-next-line-treatment (TTNT), disregarding endocrine treatments as the maintenance	12-month
Duration of therapy (DoT)	Duration of therapy (of T-DM1) will be compared to the duration of previous therapy (T-DXd) to ensure the comparability of each treatments reflecting the tumor biology and clinical course.	12-month
Incidence of Treatment-Emergent Adverse Events	Incidence of Treatment-Emergent Adverse Events	12-month

Collaborators and Investigators

• Sponsor: Seoul National University Hospital

Study record dates

Study Major Dates

• Study Start (Actual): February 26, 2025
• Primary Completion (Estimated): September 30, 2028
• Study Completion (Estimated): September 30, 2029

Study Registration Dates

• First Submitted: March 31, 2025
• First Submitted That Met QC Criteria: April 7, 2025
• First Posted (Actual): April 15, 2025

Study Record Updates

• Last Update Posted (Actual): April 23, 2026
• Last Update Submitted That Met QC Criteria: April 21, 2026
• Last Verified: April 1, 2026

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Neoplasms by Site; Neoplasms; Skin Diseases; Breast Diseases; Skin and Connective Tissue Diseases; Breast Neoplasms
• Other Study ID Numbers: H-2412-069-1597

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No