Prognostic and predictive value of HER2/neu oncogene in breast cancer.

Assessment of HER2/neu oncogene has been used as both a prognostic and predictive marker for breast cancer. However, the choice of the best method to assess the status of HER2/neu oncogene in breast cancer tissue remains controversial. A variety of techniques are available to detect HER2/neu gene amplification and overexpression. Tissue-based detection methods by immunohistochemistry (IHC) and/or fluorescence in situ hybridization (FISH) offers a clear advantage over other approaches. FISH is a costly and relatively difficult assay and yet appears to be a better predictor of response to Herceptin (Trastuzumab) therapy and patient outcome. IHC is less expensive and is easier to perform; however, it suffers from a high rate of false negativity and positivity as well as inter-observer variability among pathologists. Suggestions have been made to use IHC as a screening procedure followed by confirmation by FISH in selected cases. Considering the importance of an accurate assessment of HER2/neu oncogene in selecting therapy, a better alternative may be to use FISH as the primary testing for HER2/neu oncogene. Herceptin therapy is associated with several side effects and is expensive. Thus, in the long term, it may be more cost-effective to use the FISH procedure and reduce the possibility of under-treatment or over-treatment of breast cancer patients. In addition, assessment of HER2/neu oncogene on every newly diagnosed early breast carcinoma may not be necessary. Metastatic lesions, when they occur, can be sampled by fine needle aspiration biopsy or core needle biopsy for assessment of HER2/Neu status. Copyright 2002 Wiley-Liss, Inc.