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[184] The FISH 2002 Study: Comparison of Techniques To Assess the HER2 Status of Patients with Metastatic Breast Cancer

F Penault-Llorca, L Arnould, G MacGrogan, A Leroux, I Treilleux, M Antoine, MO Vilain, C Blanc-Fournier, F Ettore, V Fermeaux, C Charpin-Taranger, J Jacquemier, B Lannes, G Escourrou, M Lacroix-Triki, P Gosset, C Sagan, J Couturier, A Vincent-Salomon. GEFPICS, Cedex, France

Background: Immunohistochemistry (IHC) and fluorescence in situ hybridisation (FISH) can be used to assess human epidermal growth factor receptor 2 (HER2) status and identify patients with breast cancer who are eligible for trastuzumab (Herceptin) treatment. The FISH 2002 study investigated concordance between IHC and FISH performed in peripheral and regional reference centres.
Design: HER2 IHC was performed on primary breast tumours of patients presenting with metastatic breast cancer. Paraffin-embedded tumour samples and initial IHC results from peripheral centres were sent to their corresponding regional reference centres where IHC was repeated and FISH performed to determine concordance with IHC. Assessments of concordance excluded samples with equivocal IHC scores (2+ according to the HercepTest scoring system).
Results: From December 2002 until June 2006, 18 regional reference and 73 peripheral centres collected data from 1543 patients. We present here the interim analysis of the first 1153 patients. In regional reference centres, the HER2 overexpression rate (IHC 3+) was 23.6% (177/751) and 15.2% (114/751) of samples were IHC 2+. The IHC false-positive rate (IHC 3+, not amplified) was 2.3% and the false-negative rate (IHC 0 or 1+, amplified) was 1.5%. In peripheral centres, the HER2 overexpression rate was 19.2% (113/587) and 20.4% (120/587) of samples were IHC 2+. The IHC false-positive and false-negative rates were 13.5% and 3.7%, respectively. FISH analysis identified 27.4% (363/1326) of samples as FISH positive. Considering all IHC 0/1+ and 3+ cases, the rate of discordance between IHC and FISH was 2.3% (n=1153). The advantages and disadvantages of each technique will be presented at the meeting.
Conclusions: Concordance between IHC and FISH was high despite differences between centre protocols. While the rate of false negatives for IHC was low, the higher rate of false positives emphasises the need for greater accuracy of IHC testing. Quality-assurance programmes are essential in achieving high-quality HER2 testing to ensure optimal treatment for each patient.
Category: Breast

Wednesday, March 28, 2007

Poster # 4, Wednesday Morning