Dual color chromogenic in situ hybridization for determination of HER2 status in breast cancer: a large comparative study to current state of the art fluorescence in situ hybridization

Jens Mollerup,Ulla Henriksen,Sven Müller,Andreas Schønau

doi:10.1186/1472-6890-12-3

Abstract

BackgroundChromogenic in situ hybridization (CISH) is fast becoming a well established technique for easy and sensitive determination of HER2 gene status in breast cancer. However, for the chromogenic method to achieve status as a safe and reliable technique, the method needs to be validated against already known and validated FISH techniques.MethodsHere it is reported from a comparative study where HER2 gene status obtained by HER2 CISH pharmDx™ Kit was compared to HER2 gene status obtained by the FDA approved HER2 FISH pharmDx™ Kit and the PathVysion HER-2 DNA probe Kit. The study included 365 formalin fixed and paraffin-embedded invasive breast cancer tissue specimens collected consecutively at a US reference laboratory.ResultsThe data obtained revealed an overall HER2 status concordance of approximately 98% for comparisons of HER2 CISH pharmDx™ Kit to both HER2 FISH pharmDx™ Kit and PathVysion HER-2 DNA Probe Kit.ConclusionsThe concordance between results obtained using the recently FDA approved HER2 CISH pharmDx™ Kit with previously FDA approved FISH techniques for HER2 gene status determination indicate that the HER2 CISH pharmDx™ Kit is a reliable chromogenic alternative to fluorescence-based methods.

Highlights

Chromogenic in situ hybridization (CISH) is fast becoming a well established technique for easy and sensitive determination of HER2 gene status in breast cancer
The specimens were collected consecutively at a US reference laboratory and the first 304 specimens were included irrespective of HercepTestTM (Dako Denmark A/S, Glostrup, Denmark) IHC score and additional 61 specimens were included based on a IHC HER2 2+ score as determined by HercepTestTM Serial sections (5 μm) were cut from each specimen and stained with H&E, HercepTestTM for HER2 protein expresion, HER2 CISH pharmDxTM Kit (Dako Denmark A/S), HER2 FISH pharmDxTM Kit (Dako Denmark A/S) and PathVysion HER-2 DNA Probe Kit (Abbott Laboratories, Illinois, USA)
Frequencies of amplified and non-amplified specimens Frequencies of HER2 amplified and non-amplified test results found by HER2 CISH, HER2 FISH and PathVysion FISH are presented in Table 2 for all specimens

Summary

Introduction

Chromogenic in situ hybridization (CISH) is fast becoming a well established technique for easy and sensitive determination of HER2 gene status in breast cancer. Overexpression of HER2 protein and/or HER2 (Human Epidermal Growth Factor Receptor 2 Gene) amplification is observed in approximately 22% of human breast cancers [1] and has been shown to be a marker of poor prognosis [2] and to predict benefit from treatment with the antibody based drug Herceptin (Genentech, San Francisco, CA, USA) [3]. Tissue based assessment of HER2 protein expression levels is commonly achieved using immunohistochemistry (IHC), whereas tissue based analysis of HER2 amplification is mostly done by in situ hybridization (ISH) techniques either fluorescence (FISH) [4] or chromogenic (CISH or SISH) [5]. Chromogenic visualization enables bright-field microscopy and easy access to tissue morphology to directly determine the appropriate tumor area for evaluation

Methods

Results

Conclusion