Abstract P1-07-04: Comparison of HER2 expression by immunohistochemistry (IHC) using automated imaging system and fluorescence in situ hybridization (FISH). A retrospective analysis of 2853 cases:

Background: Accurate assessment of HER2 status is critical for selecting patients who will benefit from trastuzumab therapy. There is still no consensus regarding the optimal method to assess HER2 status. Computerized image analysis has been shown to provide a more accurate and objective way for quantification of HER2 expression by IHC than manual evaluation. It has been suggested that the use of image analysis may help to resolve some of the discrepancies between IHC and FISH assay. We compared the results of HER2 expression by IHC using automated image analysis with fluorescent in situ hybridization (FISH) assay. Design: Testing for HER2 expression by IHC and FISH was performed on 2853 specimens at UT Southwestern Medical Center between the years 2002 to 2011. Quantification of IHC HER2 expression was done by image analysis and scored as positive (>2.0), borderline (1.5 to 2.0) and negative. ( 2.0, 1.8 to 2.0 and Results: IHC compared to FISH Conclusion: Despite improvements in IHC testing, the FISH assay may be a better method for determining HER2 status. Factors such as tissue fixation, scoring methods and choice of antibodies may contribute to the lower specificity of IHC. In the amplified group, the gene amplification ratio correlated with protein expression, being highest in the IHC positive cases and lowest in those that were negative. Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P1-07-04.