HER2 mRNA Score From Quantitative ERBB2 mRNA Expression of Oncotype Dx : Can It Replace the HER2...

Area of Science:

• Oncology
• Molecular Diagnostics
• Biomarker Research

Background:

• Novel HER2-targeted therapies are effective for HER2-positive and HER2-low breast cancer (BC).
• Accurate quantification of HER2 status is crucial for treatment selection.
• Immunohistochemistry (IHC) is a standard method for HER2 assessment.

Purpose of the Study:

• To compare the HER2 mRNA score (HS) from the Oncotype DX (ODX) test with HER2 IHC results in estrogen-receptor positive, HER2-negative BC.
• To evaluate the accuracy of HS for HER2 quantification and its correlation with clinicopathologic characteristics.
• To assess the utility of HS in distinguishing different levels of HER2 expression.

Main Methods:

• Retrospective analysis of ODX test data from 1524 patients with ER+, HER2-negative BC.
• Comparison of HS values with HER2 IHC scores (HER2-0, HER2-low, etc.).
• Receiver operating characteristic (ROC) curve analysis to assess diagnostic utility.
• Multivariate analysis to identify associations with clinicopathologic parameters.

Main Results:

• Median HS was significantly higher in HER2-low BC compared to HER2-0 BC (P <0.001).
• HS increased significantly across HER2 IHC subgroups (P <0.001).
• ROC analysis showed acceptable utility in distinguishing HER2-0 from HER2-low (AUC=0.76) and HER2-null/ultralow (AUC=0.81), with notable overlap.
• Low Ki-67 and RS were associated with higher HS (>8.9); progesterone receptor negativity, high Ki-67, high nuclear grade, lower HS, and older age were associated with high RS.

Conclusions:

• The HER2 mRNA score (HS) demonstrates significant association with HER2 IHC results in breast cancer.
• HS correlates with key clinicopathologic parameters beyond HER2 IHC status.
• The ODX test provides valuable information for HER2 status assessment, complementing IHC findings.