Are FISH HER-2/neu Results the Same on Core Needle Biopsy and Excision in Patients with Breast Cancer?
AC Lowe, N Rao, P Shintaku, N Moatamed, SK Apple. UCLA, Los Angeles, CA
Background: HER-2/neu receptor amplification status is critical to the pathological work-up of and the guidance of therapy for breast carcinoma. Fluorescence in-situ hybridization (FISH) is the gold standard for HER-2/neu amplification evaluation, yet immunohistochemical staining (IHC) is a more widely used method due to its lower cost and easier accessibility. Multiple studies have shown FISH and IHC results to have high concordance rates. To our knowledge, a comparison between FISH results for core needle biopsy specimens (CNB) and FISH results for the subsequent excision specimens (EXC) has not yet been studied. We sought to determine the concordance rate of HER-2/neu FISH in CNB and EXC.
Design: We retrospectively evaluated the FISH and IHC results in both the breast CNB and the corresponding EXC of 125 patients with invasive carcinoma of the breast from 2002-2005. Standard breast biomarkers were performed on each specimen, including IHC for HER-2/neu receptor overexpression (0 to 3+, based on pre-ASCO 2007 evaluation criteria) as well as FISH for HER-2/neu amplification (scores of <2.0 interpreted as not amplified). The IHC were evaluated by a total of four pathologists. The FISH analysis was performed and interpreted by an independent cytogenetic lab.
Results: Comparison of FISH results of the 129 CNB to the 131 EXC of all 125 patients showed a FISH concordance rate of 92% (115/125).
FISH HER-2/neu Gene Amplification on CNB and EXC
|Concordant||115/125 (92%)||13 CNB+ EXC+||102 CNB- EXC-|
|Discordant||10/125 (8%)||6 CNB+ EXB-||4 CNB- EXC+|
The IHC results of the same CNB and EXC showed a concordance rate of 98% (122/125). Comparison of the IHC results with the FISH results for all 260 cases examined showed 95% concordance (247/260).
IHC and FISH Results of 260 Cases (129 CNB and 131 EXC)
|IHC Score||# of 260 Cases (%)||% FISH Negative (#)||% FISH Positive (#)|
|0||52 (20%)||100% (52)||0% (0)|
|1||147 (57%)||93% (137)||7% (10)|
|2||40 (15%)||70% (28)||30% (12)|
|3||21 (8%)||14% (3)||86% (18)|
Conclusions: The concordance rate of FISH and IHC (95%) in the population studied was similar to previously published results. Although the concordance rate of FISH between CNB and EXC is high (92%), it is not 100% concordant. In fact, IHC for HER-2/neu overexpression had a higher concordance rate (98%).
Tuesday, March 10, 2009 9:30 AM
Poster Session III # 51, Tuesday Morning