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Historical Perspective of HER2 Testing and Treatment in Prostate Cancer
Natalia Zamalloa1,2, Jacqueline Rose3, Coen J Lap4,5
1Department of Pathology, George Washington University, Washington, DC 20037, USA.
Abstract:
Human epidermal growth factor receptor 2 (HER2) is a molecular target of interest in prostate cancer due to its association with poor prognosis and its potential role in androgen receptor signaling. However, earlier clinical trials investigating HER2-targeted therapies, including antibodies and small molecules, have shown limited efficacy. More recent studies using the HER2 antibody-drug conjugate (ADC) trastuzumab deruxtecan (T-DXd) suggest potential therapeutic benefit in prostate cancer. However, its effective utilization requires a HER2 IHC scoring system that accurately represents HER2 expression patterns unique to prostate cancer, which is currently not established. We have developed a modified HER2 IHC scoring system that, unlike the breast and gastrointestinal tumor HER2 IHC grading scales, considers the distinct spatiotemporal expression of HER2 in prostate tumors. In this commentary, we discussed two patients with metastatic prostate cancer who were classified as HER2 IHC 3+ using our prostate cancer-specific scoring system and who demonstrated meaningful clinical responses and responded to treatment with T-DXd. We further review the historical evolution of HER2 testing in prostate cancer, as well as factors that may have contributed to the failure of previous clinical trials targeting HER2 in prostate tumors. Our aim is to highlight the need for developing a standardized HER2 IHC grading model in prostate cancer, which could improve the predictive value of HER2 IHC expression, enabling a more accurate identification of patients likely to benefit from HER2-targeted ADCs.
Insights
A new scoring system for Human Epidermal Growth Factor Receptor 2 (HER2) in prostate cancer improves patient identification for HER2-targeted therapies like trastuzumab deruxtecan (T-DXd). This system enhances treatment selection for metastatic prostate cancer.
Area of Science:
- Oncology
- Molecular Biology
- Pathology
Background:
- Human Epidermal Growth Factor Receptor 2 (HER2) is linked to poor prognosis in prostate cancer.
- Previous HER2-targeted therapies showed limited efficacy, but antibody-drug conjugates (ADCs) like trastuzumab deruxtecan (T-DXd) show promise.
- Accurate HER2 expression assessment is crucial for effective T-DXd treatment in prostate cancer.
Purpose of the Study:
- To develop and validate a modified HER2 immunohistochemistry (IHC) scoring system tailored for prostate cancer.
- To evaluate the clinical response of metastatic prostate cancer patients treated with T-DXd based on the new scoring system.
- To review historical HER2 testing in prostate cancer and identify factors limiting prior trial success.
Main Methods:
- Development of a novel HER2 IHC scoring system considering unique prostate tumor expression patterns.
- Classification of two metastatic prostate cancer patients as HER2 IHC 3+ using the new system.
- Review of past HER2 testing methodologies and clinical trial outcomes in prostate cancer.
Main Results:
- Two patients with metastatic prostate cancer classified as HER2 IHC 3+ by the new system showed significant clinical responses to T-DXd.
- The modified scoring system accounts for distinct HER2 spatiotemporal expression in prostate tumors.
- Historical analysis suggests previous HER2 trials may have failed due to inadequate scoring systems.
Conclusions:
- A standardized, prostate cancer-specific HER2 IHC scoring model is needed.
- This model can improve the predictive value of HER2 expression for T-DXd therapy.
- Accurate HER2 assessment is key to identifying prostate cancer patients who will benefit from HER2-targeted ADCs.
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