Herceptin (generic name, trastuzumab) is a monoclonal antibody (a special type of immunotherapy) that was approved by the FDA for the treatment of breast cancer with HER2 over-expression. Herceptin usually is given intravenously in an outpatient setting in clinics.
HER2 (Human Epidermal Growth Factor receptor 2; also called HER-2/neu) receptors found on the surface of cells play a key role in regulating cell growth. Some women are born with or experience a mutation of the HER2 gene during their lifetime. When the HER2 gene is altered, extra copies of the HER2 gene may be present in the cells. If extra copies of the HER2 gene are present in the cells, too many HER2 receptors may be produced on the surface of cells. This over-expression of HER2 causes cells to reproduce more rapidly than normal and may lead to breast cancer.
HER2 protein over-expression is present in approximately 25% to 30% of breast cancers. Breast cancers that over-express the HER2 gene tend to be aggressive, spread quickly to other regions of the body, and are not as responsive to standard treatments, including certain chemotherapy regimens.
Herceptin seeks out and attaches itself specifically to the HER2 protein receptor on the surface of breast cancer cells. The presence of the bound Herceptin antibody on the surface of the cancer cells leads to an immune reaction that is toxic to the cancer cells.
Furthermore, Herceptin has been shown to slow the growth and spread of breast tumors that have an overabundance of HER2 protein receptors on their surface. Thus, Herceptin can be used as one of the post-surgical treatments for women with early-stage or late-stage breast cancer that overexpressed HER2.
Two recent clinical studies demonstrated that post-surgical chemotherapy with doxorubicin and cyclophosphamide, followed by treatment with Herceptin and the chemotherapeutic, paclitaxel, lowered the rate of recurrence by 52% in women with early-stage breast cancer (with and without adjacent lymph node involvement) that overexpressed HER2, compared to the rate of recurrence of disease in women treated post-surgically with the chemotherapeutic drugs but without Herceptin.
1. Trastuzumab after adjuvant chemotherapy in HER2-positive breast cancer. New England Journal of Medicine. 2005; 353:1659-1672.