Development of a prognostic breast cancer diagnostic: Quantitative analysis of HER2 status using a multiplex bead assay on homogenized formalin fixed paraffin embedded breast tumor tissue (LB484)

Immunohistochemistry is typically used to classify breast cancer into molecular subtypes based on the presence or absence of three protein biomarkers: estrogen receptor (ER), progesterone receptor (PR), and receptor tyrosine-protein kinase erbB-2 (HER2). Tumor cells that overexpress HER2 specifically respond to the drug trastuzumab (Herceptin). HER2 can be measured semi-quantitatively by IHC, but in up to 20% of cases, IHC results are equivocal, meaning that additional testing (fluorescence in situ hybridization [FISH]) is required to distinguish clinically meaningful HER2 overexpression from normal HER2 levels. Aiming to ameliorate this situation, we developed a diagnostic assay that allows direct quantitative determination of HER2 protein concentration from formalin fixed paraffin embedded (FFPE) tumor tissue with a multiplex bead assay. We hypothesized that substantial preanalytical and analytical factors inherent in IHC methodology were contributing to the high rate of equivocal results, and that more...