Closing remarks and treatment guidelines

The human epidermal growth factor receptor HER2 or C-erbB-2/neu is a tyrosine kinase membrane receptor, which when activated, induces a phosphorylation cascade in cytoplasmic kinases leading to increased protein transcription and cellular growth. HER2 plays an important role in the biology of breast cancer, an observation that has led to the selection of HER2 as a potential target for breast cancer treatment. Trastuzumab (Herceptin) is the first anti-HER2 monoclonal antibody that has shown a survival benefit in metastatic breast cancer patients with HER2-positive tumours (Norton et al., Proc ASCO 2000 18, 127a (abstract 483)). Tumour HER2 status should no longer be ignored because of its direct implications for the optimal management of breast cancer patients. A high priority for future research is to refine and standardise HER2 testing in order to minimise false-negative results. Furthermore, this procedure would overcome current issues relating to test reproducibility between pathology laboratories and definitions of HER2 positivity. In the meantime, a HER2-positive status on testing using any approved technique has implications for clinical practice (Fig. 1). The treatment algorithm given in Fig. 1 considers the lack of level 1, evidence-based studies that demonstrate convincingly the value of HER2 as a predictive marker for resistance or sensitivity to classic forms of breast cancer therapy (Piccart et al., Eur J Cancer 2000, 36, 1755-1761). In addition, the algorithm incorporates the available data from 1999-2000, which were generated from prospective trials exploring the value of trastuzumab both as a single agent and in combination with chemotherapy.