Clinical Report: Precision Therapy Utilizing ctDNA for Trastuzumab Deruxtecan

Overview

This report details a case of a 35-year-old woman with HER2-positive metastatic breast cancer who utilized ctDNA monitoring to guide treatment decisions. The patient achieved intracranial disease control with trastuzumab deruxtecan and pyrotinib over 17 months.

Background

Brain metastases are a common complication in patients with HER2-positive metastatic breast cancer, affecting 30-55% of this population. Traditional imaging methods often detect disease progression late. Circulating tumor DNA (ctDNA) monitoring may offer a method for earlier detection of disease activity.

Data Highlights

No numerical data available.

Key Findings

• Brain metastases occur in 30-55% of patients with HER2-positive metastatic breast cancer.
• ctDNA monitoring detected disease activity approximately three months prior to radiologic evidence of brain metastases.
• Genomic profiling revealed alterations such as MET amplification and HER2 V777L mutation in the patient.
• Treatment with trastuzumab deruxtecan and pyrotinib led to intracranial disease control for 17 months.
• Drug-induced hepatotoxicity was managed with dose modifications and supportive care.

Clinical Implications

This case illustrates the use of ctDNA monitoring in treatment decisions for HER2-positive breast cancer.

Conclusion

This case exemplifies the use of ctDNA monitoring in guiding treatment decisions for patients with HER2-positive breast cancer and brain metastases.

Related Resources & Content

1. ASCO Post, 2020 -- Tucatinib Combination Extends Survival in HER2-Positive Metastatic Breast Cancer, Including Patients With Brain Metastases
2. ASCO Guideline Update, 2022 -- Management of Advanced Human Epidermal Growth Factor Receptor 2–Positive Breast Cancer and Brain Metastases
3. Nature Medicine, 2024 -- Trastuzumab deruxtecan in HER2-positive advanced breast cancer with or without brain metastases: a phase 3b/4 trial
4. npj Breast Cancer, 2024 -- Circulating tumor DNA validity and potential uses in metastatic breast cancer
5. The ASCO Post — Tucatinib Combination Extends Survival in HER2-Positive Metastatic Breast Cancer, Including Patients With Brain Metastases KEY POINTS
6. The ASCO Post — Tucatinib Combination Extends Survival in HER2-Positive Metastatic Breast Cancer, Including Patients With Brain Metastases KEY POINTS
7. The ASCO Post — Tucatinib Combination Extends Survival in HER2-Positive Metastatic Breast Cancer, Including Patients With Brain Metastases KEY POINTS
8. Management of Advanced Human Epidermal Growth Factor Receptor 2–Positive Breast Cancer and Brain Metastases: ASCO Guideline Update | Journal of Clinical Oncology
9. Trastuzumab deruxtecan in HER2-positive advanced breast cancer with or without brain metastases: a phase 3b/4 trial | Nature Medicine
10. Circulating tumor DNA validity and potential uses in metastatic breast cancer | npj Breast Cancer