Advancing Breast Cancer HER2 FISH Quality by Image Analysis.

Abstract

Background: A critically important factor in the correlation of Her2 amplification and clinical outcome in breast cancer is the quality of histologic Her2 amplification detection. FISH is the “gold standard” for HER2 amplification detection but presently most labs use manual methods which are labour intensive and restricted by analysis time to small samples (60 cells or less if amplification status appeared clear to the observer).An ideal FISH detection system should be rapid (less than 30 minutes per sample), identify HER2/neu and CEP17 copy number objectively in each cell, count sufficient cells to be representative statistically, count Her2/neu in cell clusters objectively, and have a permanent record of each cell counted. Our objective is to develop an image analysis system for Her2/neu FISH that is superior to current manual and automated methods in all the above criteria.Materials and Methods: The Visiopharm Integrator System software and a Leica DM6000B fluorescence microscope equipped with a Prior 8-slide capacity motorized stage (Mac 5000 ps system stage control) and Hamamatsu camera (Model CA4742-80-12AG) were used for image analysis. Forty breast cancer biopsies, 15 core biopsies included, were examined for Her2 FISH previously assessed manually on the same slide. For manual detection, at least 3 representative fields were selected by the observer. For image analysis, unbiased tumour sampling, typically 16 fields, was assessed within a region of interest previously identified. Methods were compared by ASCO/CAP amplification criteria and by assessment of technical time, cells counted and objectivity of counting criteria.Results:Seven discordant cases were observed. Five cases were downgraded by image analysis. Two cases, one uninterpretable manually and one seen as not amplified manually, were seen as amplified by image analysis.Discussion: Image analysis FISH with Visiopharm software allows for establishment of finite cell inclusion criteria reflecting size, circularity and other measurable cell features. Image analysis facilitates higher cell counts without observer selection bias in less time, and with smaller increases in technical time as more cells are counted. Discordance may be attributable to heterogeneity with larger sample of cells assessed and objective assessment of clusters in the image analysis method. Our image analysis protocol demonstrated successfully the quantification of HER2 in separate signals, in clusters and in split signals. HER2/CEP17 copy numbers were determined for each cell and for more cells in much less time while providing a permanent image record of all cells assessed.Image analysis has promise to improve substantially the quality of Her2 FISH assessment in breast cancer biopsies.Supported in part by an unrestricted grant from Hoffman-LaRoche Ltd.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 6015.