Trastuzumab is the generic name for the brand-name medication, Herceptin, a monoclonal antibody (a special type of immunotherapy) that was approved by the FDA for the treatment of breast cancer with HER2 over-expression. Trastuzumab 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 throughout their lifetime. When the HER2 gene is altered, extra 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 affects approximately 20% to 30% of breast cancer patients. 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.
Trastuzumab seeks out and attaches itself specifically to the HER2 protein receptor on the surface of breast cancer cells. The presence of the bound trastuzumab antibody on the surface of the cancer cells leads to an immune reaction that is toxic to the cancer cells.
Trastuzumab has been shown to slow the growth and spread of breast tumors that have an overabundance of HER2 protein receptors on their surface. Also, trastuzumab bound to the HER-2/neu receptor can help the immune system to try to rid the body of the cancer cells.
Thus, trastuzumab 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 trastuzumab 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 trastuzumab.
1. Trastuzumab after adjuvant chemotherapy in HER2-positive breast cancer. New England Journal of Medicine. 2005; 353:1659-1672.