Purpose: HER2 gene amplification and overexpression is associated with aggressive breast cancer and poor prognosis. Accurate HER2 testing of patients with breast cancer before treatment is important to ensure that as many patients with HER2-positive breast cancer as possible receive the most appropriate treatment and that women with HER2-negative disease avoid a potentially toxic therapy. This study compares immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) HER2 testing at central and regional laboratories in Greece.
Patients and methods: The HER2 status of 458 breast cancer samples was determined by IHC in central and regional laboratories using commercially available anti-HER2 antibodies. FISH analysis, scored as number of signals or a ratio, was subsequently performed by the central laboratory on most samples. Various statistical analyses were used to examine concordance between test center results.
Results: Immunohistochemistry HER2 testing was successfully performed on 445 samples in the central laboratory and 381 samples in regional laboratories, with good concordance between central and regional laboratories. After FISH analyses of a large proportion of these samples, good correlation was observed between FISH HER2 status and IHC results from the central laboratory but not from regional laboratories. These data suggest that HER2 status determined by IHC in a central laboratory is generally more accurate than that determined by a regional laboratory.
Conclusion: This study emphasizes the importance of accurate HER2 testing and the need to continually check the reproducibility and reliability of the test.