Comparison of immunohistochemistry (IHC) and quantitative RT-PCR: ER, PR, and HER2 receptor status.

47 Background: IHC is the present standard for measuring estrogen (ER) and progesterone receptor (PR) expression for breast cancer. However, the lack of concordance between testing laboratories and the critical patient treatment decisions made with results prompted ASCO/CAP to recommend guidelines and proficiency testing requirements to ensure accuracy. Quantitative RT-PCR (qRT-PCR) is an alternative method for ER and PR testing and while concordance with IHC has been reported, additional testing is merited. This study compares ER, PR and HER2 status determined by IHC and qRT-PCR. Methods: FFPE tissues of ER(+) tumors collected and tested at the Blumenthal Cancer Center were studied. Expression levels of ESR1, PGR, and ERBB2 were determined by a multiplex qRT-PCR TaqMan assay and by the Oncotype Dx assay. Pre-established cutpoints were used to determine positivity. Only samples with qRT-PCR and corresponding IHC data were used, resulting in 144 ER, 128 PR, and 107 HER2 comparisons. ESR1 and PGR expression...