Branched-chain Assay for ER, PR, and HER2 RNA Levels is a Useful Adjunct in the Evaluation of ER, PR, and HER2 in Breast Cancer

Purpose: The status of estrogen receptor (ER), progesterone receptor (PR) and HER2 is critical in patients undergoing breast cancer treatment. We performed this study to evaluate the QuantiGene Reagent System as a clinical test for detecting ER, PR, and HER2 RNA levels in formalinfixed, paraffin-embedded (FFPE) tissue. Methods: The RNA levels of ER, PR and HER2 were measured using the QuantiGene2.0 assay in FFPE tissue from breast cancer patients (n=40) and compared with ER and PR immunohistochemistry results and HER2 fluorescence in situ bybridization (FISH) results. Results: When the cut-off values for ER, PR, and HER2 RNA levels were 5.0, 7.2, and 50, respectively, the sensitivity, specificity, and positive and negative predictive value of the QuantiGene 2.0 Assay were 96.6%, 90%, 96.7%, and 90%, for ER; 89.7%, 81.8%, 92.9%, and 75% for PR; and 83.3%, 96.4%, 90.9%, and 93.1% for HER2, respectively. The Allred scores for ER and PR as well as the HER2 FISH ratio were correlated with RNA levels (p=0.046, r=0.32; p