From HER2 to herceptin.

HER2 overexpression occurs in 25% of breast cancers and seems to correlate with poor prognosis. HER2 overexpression may predict tamoxifen failure and different response rates to chemotherapeutic agents such as the taxanes and anthracyclines. The detection of HER2 and its overexpression is performed using fluorescent in situ hybridisation (FISH) and/or immunohistochemistry (IHC). Trastuzumab [Herceptin (H)] is a humanised IgG monoclonal antibody specific for the growth factor receptor HER2. Pre-clinical trials using monoclonal antibodies have shown inhibition of breast tumour growth in athymic nude mice. Phase II and III clinical trials have evaluated the efficacy and safety of Herceptin in women with metastatic breast cancer in combination with other agents and as a single agent. Currently, Trastuzumab and paclitaxel is the only combination indicated for the treatment of patients with metastatic breast cancer whose tumours overexpress HER2. It is also indicated as a single agent in women with HER2-overexpressing metastatic breast cancer that has progressed after previous chemotherapy. Herceptin is a well-tolerated drug and the side-effects that are commonly seen with chemotherapy, such as neutropenia, alopecia and mucositis, are rarely observed. The main risk factors for cardiotoxicity are concurrent or previous anthracycline exposure. The potential role of Herceptin in the adjuvant setting is currently being evaluated.