Background: The most commonly used methods for detecting HER2 gene amplifi cation in breast cancer are immunohistochemistry and fl uorescence in-situ hybridization. The aim of this retrospective study was to assess HER2 expression by real-time RT-PCR.
Material/Methods: Expression of HER2 was analyzed by real-time RT-PCR and immunohistochemistry in specimens of invasive ductal breast cancer tissue obtained from 131 women during radical mastectomy.
Results: There was a highly signifi cant difference in mean relative gene expression between HER2-positive and HER2-negative patients as assessed by immunostaining (22.10±41.89 vs. 3.17±8.76; p<0.001). With a median follow-up of 56 months, the cancer-specific survival of HER2-positive patients assessed by RT-PCR was worse in all cases and in the node-positive group. In multivariate analysis, HER2 status was an independent prognostic factor in all patients.
Conclusions: Real-time RT-PCR is a valuable method for determining HER2 status, but the selection of the cut-off point of the relative gene expression differentiating between HER2-negative and -positive tumors is essential.

Keywords: Survival Rate, Reverse Transcriptase Polymerase Chain Reaction, Receptor, erbB-2 - metabolism, Poland - epidemiology, Genes, erbB-2, Gene Amplification, DNA Primers - genetics, Carcinoma, Ductal, Breast - mortality, Breast Neoplasms - mortality, Base Sequence