Potential impact of HercepTest™ mAb PharmDx (Dako Omnis) (ge001) in breast cancer diagnosis.

The HER2 gene is a biomarker for breast cancer prognosis and treatment. Overexpression of HER2 protein determined by immunohistochemistry (IHC) or amplification of the HER2 gene determined by fluorescence in situ hybridization (FISH) is a condition for qualifying patients for anti-HER2 therapy. Due to the high toxicity of anti-HER2 treatment, proper patient selection is essential. In our study we compared 40 cases with IHC staining of HER2 antibody determined by Ventana PATHWAY anti-HER2/neu antibody (4B5) as HER2 2+ with the new antibody (HercepTest™ mAb PharmDx [Dako Omnis] [GE001]). Then using a double-blind study we compared the (IHC) evaluation with FISH results. In 65% of cases (26/40) the IHC 2+ score remained unchanged, in 32.5% of cases (13/40) expression of HER2 protein after IHC with new antibody was indicated as 3+ score, and in one case we observed a decrease of HER2 protein expression to 1+. In all cases but one, in which we found IHC HER 3+ with new antibody, there was FISH amplification. We have reason to believe that the new antibody will reduce the diagnostic time and avoid unnecessary costs. Due to the small study group, further investigation is needed.

Comparison of in situ hybridization methods for the assessment of HER-2/neu gene amplification status in breast cancer using a tissue microarray.

BACKGROUND: This project compared HER-2/neu gene status in breast cancers, as demonstrated by FISH (fluorescent in situ hybridization) and CISH (chromogenic in situ hybridization) and using a tissue microarray (TMA). The study also aimed to show whether the TMA technique could be used in clinical diagnostics, rather than remain a scientific tool. MATERIALS AND METHODS: A TMA was constructed using 121 breast cancer specimens, 6 cores from each specimen. Demonstration and assessment of HER-2/neu gene status was by FISH (Vysis Path) and CISH (DAKO Duo CISH). RESULTS: The 121 breast cancer specimens were divided into 3 groups by HER-2 status, as determined by immunohistochemistry. In the HER-2 negative group no amplification was observed in 36 out of 40 cases. 3 cases showed amplification by both methods and one by CISH alone. The equivocal HER-2 group showed no amplification in 30 out of 41 cases and amplification in 9 cases. One case was FISH negative CISH positive and one was discarded. In the HER-2 positive group, amplification was confirmed in 37 of the 40 cases by both methods. 3 cases were unsuitable for assessment. CONCLUSIONS: This study indicated that CISH is a sensitive alternative to FISH in detecting HER2 gene amplification and may replace FISH in HER2 testing. Good agreement was observed between methods (98.5% - 119 out of 121 cases). Furthermore, as only 4 out of 121 cases were unsuitable for assessment (no signal or missing TMA cores) - it may be feasible to use TMA in diagnostics.