Trastuzumab-containing regimens for metastatic breast cancer.

Patients with breast cancer are classified as having cells that over-express the human epidermal growth factor receptor 2 (known as HER2-positive) or not (HER2-negative). Typically, patients with HER2-positive disease have a worse prognosis. Trastuzumab is a selective treatment that targets the HER2 pathway. The available evidence supporting trastuzumab regimens mostly relies upon surrogate endpoints and, although the efficacy results seem to support its use, other uncertainties have been raised about its net benefit in relation to transient cardiac toxicity and a long-term increased risk of metastasis to the central nervous system.