Abstract
Determining human epidermal growth factor receptor 2 (HER2) status in breast cancer patients can be attained by fluorescent in situ hybridization (FISH) analysis, which prompts targeted treatment options. This study was performed to compare the staining results of Dako’s manual overnight HER2 FISH pharmDx™ assay with the manual (4 hours) HER2 IQFISH pharmDx™ assay and the Dako Omnis automated (4 hours) HER2 IQFISH assay, for assessment of HER2 amplification.Thirty-four formalin-fixed paraffin-embedded (FFPE) tissue blocks from patients diagnosed with invasive breast cancer were used to compare three FISH assays in three experiments. All assays included Texas Red-labeled HER2 and fluorescein-labeled centromere 17 (CEN-17) probes. First, 20 blocks with known HER2 immunohistochemistry (IHC) and FISH results from a reference laboratory were used in the validation of HER2 FISH pharmDx™ assay. Secondly, 19 of the same blocks were used in a comparison of HER2 FISH pharmDx™ assay and HER2 Instant Quality FISH pharmDx (IQFISH pharmDx™) assays. The third experiment, which included 23 blocks, compared the HER2 FISH pharmDx™ assay with the Dako Omnis IQFISH assay (stained on a Beta version of Dako’s new Omnis platform). Stained slides were counted following American Society of Clinical Oncology/College of American Pathologists (ASCO/CAP) guidelines (2007 version), with three categories of labeling: <1·8 (negative), 1·8–2·2 (equivocal), and >2·2 (positive) calculated HER2/CEN-17 ratio. The results showed high agreement between all assays employed. Initial validation of HER2 FISH pharmDx™ assay to the results provided by a reference laboratory had a concordance of 95%. The concordance between HER2 FISH pharmDx™ assay and HER2 IQFISH pharmDx™ assay was 100%. There was also 100% concordance between manual and Omnis IQFISH staining. A high level of concordance was obtained in all three experiments, indicating that manual and automated IQFISH are comparable to HER2 FISH pharmDx™. IQFISH has a faster turn-around-time (TAT) and showed comparable results in quality and quantitation.
Published Version
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