Abstract
BackgroundThe clinical benefit of determining the status of HER-2/neu amplification in breast cancer patients is well accepted. Although immunohistochemistry (IHC) is the most frequently used method to assess the over-expression of HER-2 protein, fluorescent in-situ hybridization (FISH) is recognized as the "gold standard" for the determining of HER-2/neu status. The greatest discordance between the two methods occurs among breast tumors that receive an indeterminate IHC score of 2+. More recently, a real-time polymerase chain reaction (PCR) assay using the LightCycler® has been developed for quantifying HER-2/neu gene amplification. In this study, we evaluated the sensitivity and specificity of a commercially available LightCycler assay as it compares to FISH. To determine whether this assay provides an accurate alternative for the determination of HER-2/neu status, we focused primarily on tumors that were deemed indeterminate or borderline status by IHC.MethodsThirty-nine breast tumors receiving an IHC score of 2+ were evaluated by both FISH and LightCycler® technologies in order to determine whether quantitative real-time PCR provides an accurate alternative for the determination of HER-2/neu status.ResultsWe found a high concordance (92%) between FISH and real-time PCR results. We also observed that 10% of these tumors were positive for gene amplification by both FISH and real-time PCR.ConclusionThe data show that the results obtained for the gene amplification of HER-2/neu by real-time PCR on the LightCycler® instrument is comparable to results obtained by FISH. These results therefore suggest that real-time PCR analysis, using the LightCycler®, is a viable alternative to FISH for reassessing breast tumors which receive an IHC score of 2+, and that a combined IHC and real-time PCR approach for the determination of HER-2 status in breast cancer patients may be an effective and efficient strategy.
Highlights
The clinical benefit of determining the status of HER-2/neu amplification in breast cancer patients is well accepted
The HER-2/neu status is mainly used for identifying patients with advanced breast cancer who may benefit from the therapy with anti-HER-2 antibody trastuzumab/Herceptin® (Genetech, San Francisco, CA) a humanized murine monoclonal antibody which has been shown to be effective in prolonging survival in patients with receptor positive metastatic breast carcinoma [19]
As fluorescent in-situ hybridization (FISH) is currently the "gold standard" method for evaluation of HER-2/neu amplification we wanted to examine the performance of the LightCycler Real Time polymerase chain reaction (PCR) assay as measured against FISH assay in IHC borderline cases
Summary
The clinical benefit of determining the status of HER-2/neu amplification in breast cancer patients is well accepted. To determine whether this assay provides an accurate alternative for the determination of HER-2/neu status, we focused primarily on tumors that were deemed indeterminate or borderline status by IHC. Considered to play a role in the biologic behavior or pathogenesis of human breast cancer, the amplification of the HER-2/neu gene is regarded as an established predictive [3] and prognostic [4] marker for breast cancer, for the management of advanced breast cancer. The HER-2/neu status is mainly used for identifying patients with advanced breast cancer who may benefit from the therapy with anti-HER-2 antibody trastuzumab/Herceptin® (Genetech, San Francisco, CA) a humanized murine monoclonal antibody which has been shown to be effective in prolonging survival in patients with receptor positive metastatic breast carcinoma [19]
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