Overview of treatment results with trastuzumab (Herceptin) in metastatic breast cancer.

HER2/neu amplification/overexpression confers more aggressive and malignant characteristics on breast cancer cells. Patients with HER2/neu-amplified breast cancer have a worse prognosis than those with normal HER2/neu expression. Over the past decade, the intracellular signaling pathways associated with this growth factor receptor have been elucidated. Multiple therapeutic strategies that target the HER2/neu oncoprotein are under development. Trastuzumab (Herceptin; Genentech, Inc, South San Francisco, CA), a humanized monoclonal antibody that binds to the extracellular domain of the HER2/neu receptor, has undergone phase I, II, and III clinical trials. These studies have shown that, as a single agent, trastuzumab has substantial and reproducible antitumor activity in HER2/neu-amplified metastatic breast cancer. In addition, when added to chemotherapy, trastuzumab improves antitumor efficacy as measured by time to progression, response rate, and survival. Additional chemotherapy/trastuzumab combinations are under active evaluation, and new schedules of administration are being tested. Thus, trastuzumab is the first successful example of molecularly targeted therapy in the management of metastatic breast cancer. Copyright 2001 by W.B. Saunders Company.