Metastatic extramammary Paget’s disease successfully treated by trastuzumab deruxtecan: a rare case report
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By
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Lien-Ping Chou
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Ming-Yang Lee
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Chien-Liang Fang
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Chun-Liang Tung
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I-Li Lin
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Cheng-Huang Shen
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June 24, 2026
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Clinical Scorecard: Successful Treatment of Metastatic Extramammary Paget’s Disease with Trastuzumab Deruxtecan: A Unique Case Study
At a Glance
| Category | Detail |
|---|
| Condition | Metastatic Extramammary Paget’s Disease (mEMPD) |
| Key Mechanisms | Overexpression of Her2/neu protein in approximately 40% of cases; high tumor mutation burden. |
| Target Population | Elderly patients with metastatic extramammary Paget’s disease. |
| Care Setting | Oncology and surgical intervention for rare malignancies. |
Key Highlights
- mEMPD has a poor prognosis with a 5-year overall survival rate of approximately 16%.
- HER2-targeted therapies, including trastuzumab, show promise in mEMPD treatment.
- Trastuzumab deruxtecan demonstrated partial response in a patient with low Her2/neu expression.
- High tumor mutation burden (30Muts/Mb) may influence treatment response.
- Immunotherapy effects in EMPD remain undetermined.
Guideline-Based Recommendations
Diagnosis
- Diagnosis confirmed through skin biopsy and imaging studies.
Management
- Initial treatment may include trastuzumab and pembrolizumab; consider trastuzumab deruxtecan for low Her2/neu expression.
Monitoring & Follow-up
- Regular imaging to assess treatment response and disease progression.
Risks
- Limited data on the efficacy of conventional cytotoxic regimens; potential for poor prognosis.
Patient & Prescribing Data
73-year-old male with metastatic extramammary Paget’s disease.
Initial treatment with trastuzumab and pembrolizumab showed no response; trastuzumab deruxtecan resulted in partial response.
Clinical Best Practices
- Utilize molecular profiling to guide treatment decisions.
- Consider precision oncology approaches for advanced mEMPD.
- Monitor for potential side effects of targeted therapies.
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