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HER2 Ultra-Low breast Cancer Prevalence Examined
Table of Contents
A recent study highlights the potential for more patients with advanced breast cancer to benefit from HER2-targeted therapies.
A new study presented at a major oncology conference sheds light on the prevalence of “HER2 Ultra-Low” expression in advanced breast cancer patients who were previously classified as HER2 IHC0. The research suggests that a notable proportion of these patients might be eligible for HER2-targeted therapies.
Study Overview
The study focused on assessing the prevalence of “HER2 Ultra-Low” expression, defined as faint membrane staining in >0 but ≤10% of tumor cells, by re-evaluating HER2 IHC0 biopsy slides.
“About 3 in 5 patients…met the “HER2 Ultra-Low” criteria by at least 1 pathologist, implying that a significant number of additional patients may benefit from HER2 targeted therapy.”
Methods
Researchers analyzed data from 300 patients with advanced breast cancer (stages III-IV) with clinically documented HER2 IHC0 status between January 2017 and January 2023. Biopsy slides were digitized and scanned at 40x magnification. Two pathologists independently reported HER2 status and tumor stain percentage based on 2023 ASCO-CAP guidelines. Patients were classified as “HER2 Ultra-Low” if their slide was scored as IHC0 with >0% but ≤10% staining. Cohen’s κ was used to quantify the agreement between pathologists.
Key Findings
Out of the 300 patients, 285 (95%) remained classified as IHC0 by at least one pathologist. Among these, 60% (171 patients) were determined to be “HER2 Ultra-low” by at least one pathologist. The rate of “HER2 Ultra-Low” per pathologist ranged from 43% to 45%. The overall inter-pathologist concordance was 57%; patients with no observable HER2 IHC staining accounted for the majority of the concordant patients.
Table. Concordance Among 2 Pathologists’ (P1/P2) Review of IHC Biopsy Slides
Implications
The study suggests that a significant proportion of advanced breast cancer patients initially classified as HER2 IHC0 may actually be HER2 Ultra-Low, possibly expanding the pool of patients who could benefit from HER2-targeted therapies. The researchers also noted the relatively low concordance between pathologists in identifying lower levels of HER2 expression, highlighting the need for improved precision through digital tools, artificial intelligence, enhanced training, and adherence to best practice recommendations.
Frequently Asked Questions
- What does HER2 Ultra-Low mean?
- HER2 ultra-Low refers to a faint membrane staining in >0 but ≤10% of tumor cells, as determined by immunohistochemistry (IHC) testing.
- Why is HER2 status significant in breast cancer?
- HER2 status helps determine the best course of treatment. Patients with HER2-positive breast cancer may benefit from HER2-targeted therapies.
- What are HER2-targeted therapies?
- HER2-targeted therapies are drugs that specifically target the HER2 protein, helping to slow or stop the growth of cancer cells.
