Approximately 192,000 new cases of breast cancer are diagnosed each year in the United States, according to the National Cancer Institute (NCI). Approximately 20 to 25 percent of all breast cancers are HER2-positive (human epidermal growth factor-2; HER2+), an aggressive, fast growing form.
In order to determine whether or not breast cancer is HER2-positive, meaning that the cancer overexpresses the HER2 protein, a biopsy of the breast tumor needs to be conducted. There are two types of tests that can detect the overproduction of HER2: immunohistochemisty (IHC) or fluorescence in-site hybridization (FISH).
The five-year survival rate for women with breast cancer is 90 percent. This is a dramatic improvement from a 63 percent five-year survival rate seen in the 1960s. If the breast cancer is caught and treated before it has spread to the lymph nodes or other organs (also called localized breast cancer), the five-year survival rate is 98 percent. If the breast cancer has spread to the lymph nodes, the five-year survival rate is 84 percent. If the breast cancer has spread to other organs in the body, the five-year survival rate is 23 percent.
Unfortunately, the survival rates of HER2-positive breast cancer is not the same as it is for HER2-negative breast cancer. The HER2-positive form of the disease has a greater likelihood of recurring after first remission and is associated with a decrease in survival as compared to HER2 negative breast cancer.
Currently, there are two targeted therapies that were specially designed to treat women whose tumors overexpress the HER2 protein. Herceptin (trastuzumab), a monoclonal antibody that is given intravenously, works by attaching itself on the HER2 protein that appears on the surface of the breast cancer cell. Tykerb (lapatinib), a pill, works by entering the breast cancer cell and attaching itself to the HER2 protein that is found just beneath the surface of the cell.