Journal of Medical Cases, ISSN 1923-4155 print, 1923-4163 online, Open Access
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Case Report

Volume 16, Number 6, June 2025, pages 212-221

Long Durable Response With Trastuzumab Deruxtecan Monotherapy in a Triple-Negative Metastatic Breast Cancer Patient With Human Epidermal Growth Factor Receptor 2 Mutation: A Long-Term Follow-Up and Literature Review

Figures

↓  Figure 1. Brain MRI with and without contrast showing a 4.8 × 4.2 × 4 cm well-circumscribed enhancing mass (arrow) in the superior aspect of the left and right cerebellar hemispheres. MRI: magnetic resonance imaging.
Figure 1.
↓  Figure 2. Brain MRI with and without contrast showing midline occipital craniectomy changes and interval progression in size and conspicuity of residual metastatic disease, measuring 3.4 × 2.4 cm (arrow). MRI: magnetic resonance imaging.
Figure 2.
↓  Figure 3. Brain MRI with and without contrast showing stable midline occipital postsurgical changes with interval resolution of recurrent parenchymal metastatic disease (arrows) from July 2022 (a) and March 2023 (b). MRI: magnetic resonance imaging.
Figure 3.
↓  Figure 4. Brain MRI with and without contrast showing remote midline occipital postoperative changes with hemosiderin deposition and no evidence of parenchymal metastatic disease (arrows) from March 2024 (a) and December 2024 (b). MRI: magnetic resonance imaging.
Figure 4.
↓  Figure 5. Graphical representation of clinical takeaways.
Figure 5.

Table

↓  Table 1. Summary of Important Systemic Therapies Used in CNS Metastatic Breast Cancer
 
Drug class Agent Indication/subtype CNS activity
ADCs: antibody-drug conjugates; CNS: central nervous system; HER2: human epidermal growth factor receptor 2; PARP: poly ADP ribose polymerase; TKIs: tyrosine kinase inhibitors.
ADCs Trastuzumab deruxtecan (T-DXd) HER2-positive and HER2-low High intracranial response rate in active brain metastases
Trastuzumab emtansine (T-DM1) HER2-positive Modest CNS activity, less effective than T-DXd
TKIs Tucatinib (with trastuzumab + capecitabine) HER2-positive, active/stable CNS metastases Strong CNS activity; improves overall and progression-free survivals
Lapatinib (with capecitabine) HER2-positive (limited use currently) Modest CNS activity
Neratinib (with capecitabine) HER2-positive, progressive CNS metastases Variable intracranial response rates
Pyrotinib HER2-positive Promising CNS activity in early-phase trials
PARP inhibitors Olaparib BRCA-mutated HER2-negative (especially triple-negative breast cancer) Some CNS penetration, modest benefit
Talazoparib BRCA-mutated HER2-negative Limited CNS-specific data