A comparative assessment of HER2 status in operable breast cancer by real-time RT-PCR and by immunohistochemistry.

Background: The most commonly used methods for detecting HER2 gene amplification in breast cancer are immunohistochemistry and fluorescence 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 significant 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.