HER2 Status
The HER2 (Her2/neu, c-erb-2 or erb-2) gene produces a protein that acts as a receptor on the surface of all cells. This receptor is sensitive to a growth factor, a signal to the cell to grow. Some cancer cells have more receptors than normal, which means they are receiving more messages to grow and divide.
There are two ways to measure HER2 status. One is an immunohistochemistry (IHC) test, which measures the over-expression of the protein (number of receptors on the surface of the cancer cell) and is reported using the numbers 0 to +3. Scores of 0 and +1 are HER2 negative and +2 and +3 are HER2 positive.
The other method of testing is fluorescent in situ hybridization (FISH), which measures the amplification of the HER-2 gene (the number of copies of the HER-2 gene present in a cancer cell). The results of this test are reported as positive or negative. HER2 positive status is associated with tumors that are fast growing and aggressive. Only 25% to 30% of women with breast cancer are HER2 positive.
The American Society of Clinical Oncology (ASCO) recommends that all women diagnosed with breast cancer should have tumor marker tests, which can be performed on cells of a tissue sample from a newly biopsied or stored tumor. Tumor marker testing can help predict how a tumor may behave.
Herceptin
Herceptin® (trastuzumab) is the only FDA-approved therapy for women with metastatic breast cancer whose tumors express too much HER2 protein. It is also approved for adjuvant use (treatment following primary therapy, such as surgery) in combination with paclitaxel, and as a single agent for those who have received one or more chemotherapy regimens. Herceptin is not chemotherapy. It is a monoclonal antibody (sometimes called biologic therapy).
Herceptin administration can result in the development of certain heart problems, including congestive heart failure. Severe allergic reactions, infusion reactions, and lung problems have been observed. These rarely have been fatal.
