Breast cancer with too much HER2 protein can grow more quickly and spread to other body parts. Your doctor may test your tumor tissue for HER2 to help plan your treatment. An IHC test can result in zero, one, or two, with a score of two being equivocal (borderline). Your doctor may also do a FISH test to look for extra copies of the gene that makes HER2. This information helps doctors know whether your cancer is HER2 positive.
What is HER2?
The HER2 gene provides instructions for a protein that helps breast cells grow and divide. Cancer cells with too much HER2 protein can grow and spread faster than normal breast cells. Cancers that have too much HER2 are called HER2-positive or over-express HER2. HER2-positive cancers tend to be more aggressive but respond better to treatment with drugs targeting HER2. About 20% of all breast cancers are HER2-positive. HER2+ tumors are also more common in younger women and tend to be larger at diagnosis. They are more likely to recur and have higher rates of death. Doctors can identify HER2 status by testing a sample of your tissue during a procedure called a biopsy. The test looks for the HER2 gene or protein in your cancer cell. Your doctor may also recommend a blood test to measure the levels of HER2 protein in your body. The results of the HER2 test can change over time, so your doctor will retest your HER2 status after surgery or if you have any new symptoms. You should also ask your doctor if you are at risk of developing HER2-positive breast cancer and whether you should have regular screenings. Discussing genetic factors with your doctor is essential because hereditary breast and ovarian cancer can increase your risk of developing HER2-positive cancer.
How do I know if I have HER2?
HER2 testing is done on a cancer tissue sample from a biopsy, usually a needle or surgical biopsy. There are two ways to test HER2: immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH). These tests look at the amount of HER2 protein in the cancer cells. They can also tell if the cancer cells have extra copies of the HER2 gene, called overexpression or amplification. HER2 status can significantly affect treatment recommendations and decisions. For example, HER2-positive breast cancers can be treated with drugs that target HER2. The type of therapy you receive depends on your tumor’s HER2 status. The HER2 gene can be overexpressed in other types of cancer, such as ovarian and lung cancers. It would be best to get your cancer tested and treated at a center that sees HER2-positive patients often. This will help ensure that your cancer is diagnosed correctly and you’re given the most effective treatment. Women with HER2-positive breast cancer are more likely to have larger tumors and a higher chance of cancer returning after treatment. Women with HER2-positive in situ breast cancers may be treated with surgery, chemotherapy, and HER2-targeted therapies. If your breast cancer is HER2-negative, it’s still important to talk with your doctor about your risk.
What are the symptoms of HER2?
HER2 (also known as HER2/neu) is a protein that cancer cells can make in more significant than-normal amounts. When HER2 is overexpressed, it can cause breast cancer to grow more quickly and spread to other parts of the body. Testing for HER2 can help your care team plan your treatment. Your doctor may also use medicines that target HER2 to fight tumors. About 13 percent of all invasive breast cancers in the United States are HER2-positive. This type of cancer tends to grow more rapidly than other types and is more likely to spread, but some treatments can help. Your doctor can test your cancer for HER2 when it is first diagnosed, either by using tissue from your biopsy or after you have surgery. Doctors can test the HER2 status of your tumor by looking at a sample of your tumor tissue under a microscope. An immunohistochemistry (IHC) test looks for the HER2 protein and gives each tumor a score of zero, one, two, or three. If the IHC result is equivocal (score of two), doctors can perform more testing, such as fluorescence in situ hybridization (FISH) or another biopsy, to clarify the results.
What are the treatments for HER2?
A gene and protein called HER2 have long been linked to breast cancer. The discovery of this link spurred research to find treatments that target HER2 and kill cancer cells while sparing healthy cells. This has significantly improved survival for women with HER2-positive breast cancer. Treatments that bind to and block the activity of the HER2 protein are called trastuzumab and Herceptin. These drugs are given as injections, either intravenously or by subcutaneous (under the skin) administration. They are part of standard HER2-directed early and metastatic breast cancer therapy. They are also given as a pre-surgery (neoadjuvant) treatment for people with locally advanced breast cancer at high risk of recurrence12. Other HER2-targeted therapies include the tyrosine kinase inhibitors pertuzumab and neratinib. Pertuzumab, a monoclonal antibody targeting HER2, is available in injectable and intravenous forms. It is commonly given with chemotherapy and is often a neoadjuvant treatment before surgery in early-stage breast cancer. It is combined with chemotherapy as a first-line treatment for metastatic breast cancer. Neratinib, a tyrosine kinase inhibitor, is also available in intravenous and oral forms. It was recently approved to treat HER2-low metastatic breast cancer in people who have received two or more prior HER2-targeted therapies. It carries a low risk of lung problems and can be given at home, reducing the need to stay in the hospital.