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Discordance of HER2 Expression and/or Amplification on Repeat Testing.
Timothy P DiPeri1, Kathleen Kong2, Kaushik Varadarajan1
1Department of Surgical Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
Molecular Cancer Therapeutics
|June 20, 2023
Summary
HER2 status discordance is common in solid tumors, particularly with HER2 2+ results. Repeat biomarker testing may be valuable before HER2-targeted therapy decisions.
Area of Science:
- Oncology
- Pathology
- Biomarker Analysis
Background:
- Accurate HER2 (Human Epidermal growth factor Receptor 2) status is critical for guiding targeted therapy in solid tumors.
- Discordance in HER2 testing can significantly impact treatment selection and patient outcomes.
Purpose of the Study:
- To evaluate the rate and patterns of HER2 status discordance in patients with solid tumors undergoing central reevaluation.
- To assess the impact of biopsy type and intervening therapies on HER2 status concordance.
Main Methods:
- Central HER2 immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) testing were performed on archival or fresh biopsies from 70 patients.
- Patients had previously identified HER2 expression (IHC) or amplification (FISH/NGS) on local testing.
- Discordance was analyzed based on local versus central testing results, biopsy type, and treatment history.
Main Results:
- HER2 status discordance was observed in 30.8% of patients with HER2 overexpression/amplification who underwent new biopsies.
- Among patients with local HER2 3+ IHC, 30% showed discordance centrally (2+ or lower).
- Discordance was higher in patients who received HER2-targeted therapy (33.3%) compared to those who did not (23.8%).
Conclusions:
- Discordance in HER2 status is a significant issue in solid tumors, especially for cases with initially equivocal (2+) results.
- Repeat central biomarker evaluation is recommended, particularly when considering HER2-targeted therapies, to ensure accurate patient stratification.
