Extramammary Paget's disease (EMPD) is a rare malignant adenocarcinoma that often presents significant management challenges. When the disease becomes invasive or metastatic, the prognosis is typically poor. Currently, no standardized global care exists for inoperable cases. Nevertheless, research indicates that HER2 inhibitors for EMPD are becoming vital tools. Approximately one-third of these tumors overexpress the HER2/ERBB2 protein, which makes them susceptible to targeted therapies.

A comprehensive literature review recently analyzed 70 cases involving 92 therapeutic lines. This study assessed the efficacy and safety of various treatments, including monoclonal antibodies, tyrosine kinase inhibitors, and antibody-drug conjugates. Trastuzumab emerged as the most frequently utilized agent. Importantly, the study found that patients achieved a median progression-free survival (PFS) of 12.5 months when using these inhibitors as first-line therapy.

Evaluating Efficacy of HER2 Inhibitors for EMPD

The results show that combination therapy often yields the best outcomes for patients. Individuals receiving a HER2 inhibitor alongside chemotherapy experienced a median PFS of 13.3 months. Conversely, those on monotherapy showed a median PFS of 12 months. Furthermore, these targeted agents displayed excellent tolerability across the study population. Consequently, they represent a viable option for patients even after initial treatments fail.

Clinical protocols should now prioritize HER2 testing for all advanced EMPD cases. Clinicians should use immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) to identify overexpression. Ideally, testing should occur in both primary and metastatic sites. Moreover, testing for ERBB2 mutations is advisable, particularly when IHC does not show overexpression. Therefore, comprehensive molecular profiling helps guide personalized treatment strategies for this rare malignancy.

Frequently Asked Questions

What is the most common HER2 inhibitor used for EMPD?

Trastuzumab is the most widely reported HER2 inhibitor used in the management of advanced extramammary Paget's disease, either as monotherapy or in combination with chemotherapy.

Is molecular testing necessary for all EMPD patients?

Testing for HER2 overexpression and ERBB2 mutations is highly recommended for all patients with advanced, locally advanced, or metastatic EMPD to determine eligibility for targeted therapy.

Disclaimer: This content is for informational and educational purposes only... Refer to the latest local and national guidelines for clinical practice.

References

1. Piroth M et al. HER2 inhibitors in the management of HER2-positive extramammary Paget's disease: a literature review. Ann Dermatol Venereol. 2026 Jun 02. doi: undefined. PMID: 42229003.


2. Tanaka R, Dash S. Targeted Therapy in Rare Skin Cancers: Focus on EMPD. Indian J Dermatol. 2024;69(2):112-118.


3. Gondo T, et al. Trastuzumab-based chemotherapy for metastatic extramammary Paget's disease. Int J Clin Oncol. 2023;28(5):650-657.