Determination of HER2 gene status by fully automated fluorescence microscopy.

Objective: To examine fluorescence in situ hybridization (FISH) in HER2 amplification in response rates to trastuzumab therapy and both taxane and anthracycline-based chemotherapy regimens.

Study design: A total of 400 tumor sections were analyzed over an 8-month period. The sections were hybridized with probes for the HER2 gene and chromosome 17 centromere using standard FISH methods and analyzed on an automated fluorescence microscopy system.

Results: Reliable and valid methods for identification of the patients that will respond to treatment with trastuzumab are needed in order to achieve maximum therapy efficacy and maintain cost efficiency. FISH-based analysis is potentially an objective and reproducible approach to determination of HER2 gene status; however, manual FISH counting is a laborious task and subject to inter and intraobserver variability.

Conclusion: The system described in this paper is a valuable tool in providing a consistent approach to the interpretation of breast tumor tissue analyzed by FISH analysis. In addition to consistency, an automated system provides a record of the images produced that can be of immediate benefit in multiple review of a difficult or equivocal case and long-term benefit in terms of providing a permanent case record.