Purpose: The human epidermal growth factor receptor-2 (HER2) is overexpressed in breast cancer. The subset of patients with breast cancer demonstrating a HER2-positive status has aggressive tumors and a poor prognosis. Knowledge of the HER2 status is prerequisite when considering a patient´s eligibility for anti-HER2 targeted therapy (HerceptinⓇ). There are several assays available for determining the HER2 status. The aim of this study was to compare and evaluate the HER2 status in breast cancer by means of immunohistochemistry (IHC), FISH and real-time PCR.
Methods: DNA samples from fresh tumor tissues of 20 patients with breast cancer were analyzed with real-time PCR, using the LightCycler-HER2/neu PCR assay. A tissue microarray, containing 20 samples obtained from formalin- fixed, paraffin-embedded tissues, was used for IHC and FISH (PathyVysionTM).
Results: The frequencies of HER2 gene amplification for real-time PCR and FISH were 35 and 65% respectively, and the IHC frequency of overexpression was 70%. This study showed 75% concordance between IHC vs. FISH, 65% between IHC vs real-time PCR and 70% between FISH vs. real-time PCR. Considering real-time PCR as the gold standard, this study showed sensitivities and specificities of 100 and 46.2% for IHC, and of 100% and 53.8% for FISH.
Conclusion: These results demonstrated marked discordance for the HER2 stati according to the various methods used. IHC, a familiar cost-effective test, will undoubtedly remain in routine clinical practice for HER2 screening but confirmatory HER2 testing using either FISH or real-time PCR is recommended for indeterminate cases. Real-time quantitative PCR for HER2 appears to be clinically useful due to its simplicity and ability to produce rapid results.
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