Herceptin Metastatic Breast Cancer Treatment

December 1998 -- Herceptin (trastuzumab) is the newest drug for the management of metastatic breast cancer (breast cancer that has spread beyond the breast). It is a new type of drug and has a different mechanism of action than any other drug used to treat breast cancer.

Most cells in the body, including breast cancer cells, are dependent for their growth on growth factors, proteins that are made by cells in the body and then circulate in the blood. The circulating growth factors bind to protein receptors on cells and stimulate them to grow. Approximately 25-30% of breast cancers overexpress (have higher than normal amounts of) a receptor for an important growth factor called HER2 protein. Herceptin is a synthetic (man-made) antibody which binds and blocks the HER2 protein on breast cancer cells so that circulating growth factor cannot bind and stimulate the breast cancer cells to grow. Herceptin is given as an intravenous injection.

Herceptin is approved by the Food and Drug Administration (FDA) for use alone or in combination with another drug, paclitaxel, in the treatment of metastatic (disseminated) breast cancers that overexpress HER2. Therapy with Herceptin alone is reserved for patients who have received other chemotherapy regimens, and combination therapy is used in patients who have not previously received chemotherapy. Herceptin is effective only in the treatment of tumors that overexpress HER2.