The Efficacy of Combined Peripheral Blood CTCs and Serum HER2 Detection in Docetaxel-based Treatment for HER2 Low-expression Breast Cancer

A Prospective, Multicenter Clinical Study on the Efficacy Correlation of Deruxtepruzumab Treatment for Advanced Breast Cancer With Low/Ultra-low HER2 Expression, Guided by Peripheral Blood CTCs/CTECs Combined With Serum HER2 Detection

This study is a multicenter, double-cohort clinical research aimed at systematically evaluating the value of jointly detecting the HER2 expression of CTCs/CTECs and the serum HER2 ECD level in predicting the efficacy of T-DXd treatment for patients with HER2 low expression (IHC 1+ or IHC 2+/ISH-) and HER2 IHC 0 advanced breast cancer.

Study Overview

• Status: Not yet recruiting
• Conditions: Patients With Low HER2 Expression (IHC 1+ or IHC 2+/ISH-) and HER2 IHC 0 Advanced Breast Cancer
• Intervention / Treatment: Drug: Anti-HER2-ADC drug Deruxtepracabine

Detailed Description

The study plans to include 100 patients and divide them into cohort A (HER2 low expression, 70 cases) and cohort B (HER2 IHC 0, 30 cases) based on the tissue HER2 status. This study adopts a non-random design, and patients will be directly included in the corresponding cohort according to their baseline tissue HER2 status. All enrolled patients will receive standard T-DXd treatment after signing the informed consent form until disease progression, occurrence of intolerable toxic reactions, or study termination. The primary endpoint of the study is to explore the correlation between the HER2 expression status of CTCs/CTECs and ORR. The secondary endpoints include the correlation between the baseline HER2 expression status of CTCs/CTECs and the DCR, PFS, and OS of the entire population; the correlation between the baseline serum HER2 ECD level and the ORR, DCR, PFS, and OS of the entire population; and the ORR and PFS of each cohort. Patients will be followed up from the first administration and samples of peripheral blood will be collected for biomarker dynamic monitoring before treatment, at 2 cycles of treatment, and at the time of disease progression (the number of tests may be increased or decreased according to the patient's condition) until disease progression, death, loss to follow-up, or study closure.

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

Contacts and Locations

• Study Contact: Name: Yehui Shi Yehui Shi, Doctor of Medicine; Phone Number: +8618622221183; Email: shiyehui@tjmuch.com

Participation Criteria

Eligibility Criteria

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

• Sampling Method: Non-Probability Sample

Study Population

This study focused on breast cancer patients who had received treatment with anti-HER2-ADC drugs.

Description

Inclusion Criteria:

1. Patients with a pathological record of breast cancer;
2. Group A: Diagnosed with low expression of HER2 (IHC 1+ or IHC 2+ and ISH-); Group B: Diagnosed with HER2 0 expression (IHC 0);
3. No history of other malignant tumors;
4. Signed the informed consent form at the age of 18 or above;
5. Possess relatively complete clinical case characteristic data.

Exclusion Criteria:

• 1. Male breast cancer patients; 2. Pregnant or breastfeeding; 3. Patients known to have an allergic reaction to the active substances or any excipients of T-DXd; 4. Patients judged by the investigators to be unsuitable to participate in this study.

Study Plan

How is the study designed?

Number of groups / cohorts

1

Cohorts and Interventions

Group / Cohort

Intervention / Treatment

Low expression of HER2; Patients with low HER2 expression (IHC 1+ or IHC 2+/ISH-) and HER2 IHC 0 advanced breast cancer

Drug: Anti-HER2-ADC drug Deruxtepracabine; By monitoring the levels of CTCs/CTECs and serum HER2 expression in breast cancer patients receiving anti-HER2-ADC treatment during the treatment process, we aim to determine the therapeutic monitoring value of CTCs/CTECs and serum HER2 in these breast cancer patients using anti-HER2-ADC drugs.; Other Names: Other medications: The doctor will determine the administration plan based on the specific circumstances.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Evaluate the correlation between the HER2 expression status of baseline CTCs/CTECs and the overall response rate (ORR) of the entire population.	Evaluate the correlation between the HER2 expression status of baseline CTCs/CTECs and the overall population's DCR, PFS, and OS. Evaluate the correlation between the baseline serum HER2 ECD level and the overall population's ORR, DCR, PFS, and OS.	through study completion, an average of 2 year

Collaborators and Investigators

• Sponsor: Tianjin Medical University Cancer Institute and Hospital

Study record dates

Study Major Dates

• Study Start (Estimated): June 15, 2026
• Primary Completion (Estimated): October 1, 2030
• Study Completion (Estimated): January 1, 2031

Study Registration Dates

• First Submitted: June 8, 2026
• First Submitted That Met QC Criteria: June 24, 2026
• First Posted (Actual): June 26, 2026

Study Record Updates

• Last Update Posted (Actual): June 26, 2026
• Last Update Submitted That Met QC Criteria: June 24, 2026
• Last Verified: June 1, 2026

More Information

Terms related to this study

• Other Study ID Numbers: BC-HER2 test

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