Human epidermal growth factor receptor 2 testing: where are we?

In this issue of Journal of Clinical Oncology, Baehner et al have reported from a Kaiser Permanente case-control study that there is a high degree of concordance (97%) between quantitative reverse transcription polymerase chain reaction (qRT-PCR) and central laboratory fluorescent in situ hybridization (FISH) assessment of HER2 status. This provides us the opportunity to examine the status of human epidermal growth factor receptor 2 (HER2) testing today. For the most part, cancer is a genetic disease, and successful treatment of breast cancer is particularly dependent on a number of complex factors, including detection of the tumor early in the course of development, accurate assessment of the right biomarker, and the biology of the underlying disease. Amplification and overexpression of the HER2/ERBB2 oncogenes are observed in 15% to 25% of invasive breast cancers. HER2-positive tumors define a clinically important breast cancer subgroup that is generally associated with poor prognosis and variable response to conventional systemic cytotoxic therapy. HER2 testing is routinely performed in patients with a new diagnosis of invasive breast cancer. Accurate testing to identify HER2 status for patients with breast cancer who can benefit from anti-HER2 treatment (eg, trastuzumab, lapatinib) is a clinical and economic necessity (Fig 1). As a consequence, issues relating to accurate and reliable laboratory assessment of HER2 status in patients with breast cancer are a matter of significant concern to patients, pathologists, and oncologists.