Concordance Between Semiquantitative Immunohistochemical Assay and Oncotype DX RT-PCR Assay for Estrogen and Progesterone Receptors

Estrogen receptor (ER) status is a strong predictor of response to hormonal therapy in women with breast cancer. Not only presence of ER, but also level of expression has been shown to correlate with time to recurrence in patients undergoing therapy with tamoxifen or anastrozole. In addition, risk reduction occurs in ER-negative, progesterone receptor (PR)-positive patients treated with hormonal therapy. Immunohistochemistry (IHC) has been the method of choice for determining hormone receptor status. Recently, Genomic Health began reporting ER and PR status measured quantitatively by reverse transcription-polymerase chain reaction (RT-PCR) as a component of its Oncotype DX assay. As part of our quality assurance program, we reviewed 80 breast cancer cases that had been evaluated by the Oncotype DX assay and also underwent immunohistochemical staining for ER and PR. We found excellent correlation between ER and PR status determined qualitatively by each method. In addition, when hormone receptor expression measured quantitatively by RT-PCR and semiquantitatively by IHC were compared, results showed linear correlation. Given the additional advantages of hormone receptor IHC performed on intact tissue sections, currently there is no definitive reason to switch to RT-PCR for determination of ER and PR expressions.