Abstract P1-07-02: New high-quality HER2 IQFISH pharmDx™ assay with a ½ working day procedure and high concordance to HER2 FISH pharmDx™
Authors: Jensen Kristian , Nielsen Kirsten Vang , Andresen Lena , Müller Sven , Mollerup Jens , Matthiesen Steen Hauge , Schønau Andreas 
Published: August 2014

Introduction: HER2 assessment for selection of patients that may benefit from HER2 targeting treatment can be performed by either immunohistochemistry (IHC), fluorescence or chromogen in situ hybridization (FISH or CISH). FISH is a robust and reliable technique for direct visualization and quantitative determination of gene amplifications, deletions and translocations in human cancer cells, but FISH protocols are time-consuming and involve toxic reagents. By introducing a new non-toxic ethylene carbonate based hybridization buffer that perform with very short hybridization times, the total FISH assay time on breast cancer tissue sections can be reduced from the traditional 16–20 hours to 3½–4½ hours.

Material and methods: The new Dako HER2 IQFISH pharmDx™ was compared with Dako HER2 FISH pharmDx™ in a comparative study on 120 breast cancer specimens, and reproducibility of the HER2 IQFISH pharmDx™ assay was investigated in a study comprising 3 different sites and a total of 6 different observers. Samples for the comparative study was evaluated by Dako HercepTest™ to include all IHC scoring groups (0, 1+, 2+, 3+). Slides were stained according to manufacturer's instructions using microwave oven for heat pretreatment and RTU pepsin for 3–5 minutes at 37 °C. Hybridization was performed for 2 hours when using HER2 IQFISH pharmDx™ and for 17–20 hours when using HER2 FISH pharmDx™ Kit. All slides were blinded before evaluation. HER2 status was classified as “Non-amplified” when the HER2/CEN17 ratio &lt; 2.0 and “Amplified” when the HER2/CEN17 ratio ≥ 2.0.

Results: The new non-toxic hybridization buffer introduces a major safety improvement since formamide is no longer needed. Significantly shorter hybridization times are required to generate the same signal intensity (1–2 hour hybridization versus overnight). HER2 IQFISH pharmDx™ was compared with the traditional HER2 FISH pharmDx™ in a comparative study on 120 breast tissue specimens of human breast carcinoma. The preliminary data on HER2 status for 78 patients obtained by the two assays gave an overall agreement of 98.7% with lower and upper 95% confidence limits at 94.2% and 99.9%. The Kappa value was 0.96 (95% CL: 0.89–1.00). The p-value for McNemars test was 1.00 indicating absence of bias between the two assays. Disagreement between the two assays was observed for one specimen - a heterogeneous tissue with a small amplified area. Data from the reproducibility study that included site-to-site variation, day-to-day variation and inter-observer variation showed that the assay has a high degree of reproducibility.

Conclusion: The validation studies of the new HER2 IQFISH pharmDx™ showed a very high concordance to the traditional HER2 FISH pharmDx™ and also that the assay is robust and reproducible. Reduction of the overall assay time from a two-day to a half-day procedure for HER2 FISH, offers more flexible laboratory routines and same day reporting for all working days of the week, which could be used for fast and simultaneous FISH and IHC answers and improved patient care. Taken together, the study demonstrates the potential of a new revolutionary platform that enables optimization and acceleration of FISH analysis to the benefit of cancer patients and laboratory personnel.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P1-07-02.