her2+ patients who could benefit from herceptin may be missed by testing

[Lani]

in Belgium, at least they have been critically reviewing their ability to correctly determine her2 status



Results of a Belgian multicenter retrospective study to determine the incidence of HER2 gene amplification in patients scored as immunohistochemistry 0 or 1+.


Sub-category:
HER2+

Category:
Breast Cancer - HER2/ER

Meeting:
2011 ASCO Annual Meeting

Abstract No:
549

Citation:
J Clin Oncol 29: 2011 (suppl; abstr 549)


Attend this session at the
ASCO Annual Meeting!
Session: Breast Cancer - HER2/ER

Type: General Poster Session

Time: Monday June 6, 1:00 PM to 5:00 PM

Location: McCormick Place Hall A

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Author(s): D. Larsimont, C. Colpaert, R. Salgado, N. Vermeesen, V. D'hondt, T. De Celle; Jules Bordet Institute, Brussels, Belgium; St Augustinus, Antwerp, Wilrijk, Belgium; Institut Jules Bordet, Université Libre de Bruxelles, Brussels, Belgium; Roche Diagnostics, Brussels, Belgium; Roche Pharmaceuticals, Brussels, Belgium


Abstract Disclosures


Abstract:

Background: Human epidermal growth factor receptor 2 (HER2) is overexpressed in approximately 10% to 25% of breast cancers and is linked with aggressive tumor growth and poor prognosis. Accurate identification of HER2-positive disease is critically important to ensure these patients benefit from effective HER2-targeted therapy. In Belgium, tumors identified as immunohistochemistry (IHC) 2+ or 3+ are retested using in situ hybridization (ISH). Reimbursement of HER2-directed therapy is provided for patients with a positive ISH result (defined in Belgium as HER2/chromosome 17 ratio of > 2.0). The objective of this study was to determine the proportion of patients who are not currently retested (i.e. IHC 0/1+) but who are HER2-positive by silver in situ hybridization (SISH). Methods: Participating laboratories (33 peripheral and one central) each completed a HER2 testing questionnaire. Retrospectively collected tumor samples with a score of IHC 0/1+ from patients with primary or metastatic breast cancer were reanalyzed using Ventana INFORM HER2 DNA and chromosome 17 probes (Roche Tissue Diagnostics). Samples with a HER2/chromosome 17 ratio of > 2.0 were considered HER2-positive. Results: Results of the questionnaire showed that methods of IHC testing varied between participating laboratories: 85% used a “home-brew” assay, 12% used a CE-IVD IHC testing kit, and for 3% this information was not available. Of those samples collected for SISH, 472 (90.8%) were evaluable and 16 samples were in situ cancers that were excluded from analysis. HER2-positive status was detected in 3.1% (n=14 of 456) of samples in total, including 2.5% (n=4 of 163) of samples classified as IHC 0, and 3.4% (n=10 of 293) of samples classified as IHC 1+. Conclusions: The findings of this study suggest that IHC testing may result in false negatives. Last year in Belgium approximately 6,800 patients were categorized as IHC 0/1+. If the results of our study are representative of centers across the country, approximately 200 of these patients may be HER2-positive by SISH and may benefit from HER2-targeted therapy. A prospective trial is currently in progress to validate these results.