Current use of HER2 tests

Reliable detection of HER2 overexpression is important for the success of t rastuzumab (Herceptin(R)) therapy. Several methods are available for measur ing HER2 expression at the DNA, RNA or protein level. The method most frequ ently employed is immunohistochemical (IHC) detection of the HER2 receptor in paraffin sections. Advantages include the precise localization of the HE R2 protein, the availability of paraffin material and the ease of the proce dure. However, IHC can be influenced by the sensitivity/specificity of the antibody, tissue treatment and, in particular, subjective assessment. These disadvantages do not exist in the detection of gene amplification by fluor escence in situ hybridization (FISH) or polymerase chain reaction. However, FISH requires expensive equipment that is not widely available in patholog y laboratories. Another approach quantitates shed HER2 antigen in the serum by an enzyme-linked immunosorbent assay. The key advantage of this method is the ease of sampling blood, however, serum HER2 concentrations do not ac curately reflect the tumor status. Furthermore, this method does not regist er single-cell expression, which is important for therapeutic decision maki ng. For routine diagnostics, the combination of IHC and FISH is useful. In addition to improving the accuracy and comparability of HER2 assays, these optimized protocols may further enhance the efficacy of trastuzumab therapy by selecting those patients most likely to respond.