Pharmacogenomic analysis aspires to identify individuals with specific genetic 
characteristics in order to predict a positive response or reduce a negative 
response to a therapeutic modality. While the search continues for the many 
single nucleotide polymorphisms which will be used in such genetic analyses, 
other genetic alterations in specific cell types have proven useful in 
determining the potential for response to therapy. One such genetic alteration 
is amplification of entire gene sequences which results in overexpression of a 
gene product or protein. Amplification of the HER2 (neu, erbB-2) oncogene is 
found in up to 35% of human breast cancers and is associated with a poor 
prognosis. In addition, this genetic alteration may predict response to various 
therapeutic modalities. Assays are available to detect the HER2 protein receptor 
or copies of the HER2 gene sequence to determine eligibility for Herceptin 
treatment or adriamycin treatment in node positive patients, respectively. This 
model represents a somatic event used in the functional determination of a 
therapeutic strategy.