HER2 Positive Breast Cancer
Human epidermal growth factor receptor 2 (HER2) is a gene that makes HER2 proteins, which are receptors on breast cells. These receptors are found in normal breast tissue. They control how breast tissue grows and repairs itself.
In some cases, there are too many HER2 receptors. This is called overexpression. These extra HER2 receptors cause breast cells to grow more quickly and out of control, forming a tumor. HER2 positive (HER2+) breast cancers tend to grow quickly and may recur (come back) more often. About 1 out of every 5 breast cancers are HER2+. HER2+ breast cancer can also be hormone receptor (HR) positive, meaning the tumor needs estrogen and/or progesterone to grow.
How do I know if my cancer has too much HER2?
After a breast biopsy or surgery, a sample of the tumor is tested for extra HER2. This result can be found in your pathology report. There are two tests for HER2: the immunohistochemistry (IHC) test and the FISH test (fluorescent in situ hybridization). The results of these 2 tests are shown differently in your pathology report.
- The IHC test looks for overexpression of the HER2 protein. The result is reported as a number from 0 to 3+.
- HER2 negative can be either zero or 1+. HER2 positive can be either 2+ (borderline) or 3+.
- The FISH test checks the tumor for extra copies of the HER2 gene. The result is reported as positive or negative.
IHC is faster and less expensive, so it is often the first test done. Patients with a 2+ (borderline) result on IHC should have the FISH test done to see if the borderline result is positive or negative.
If your breast cancer recurs, talk with your provider about re-testing your tumor. Research has shown that HER2 status can change over time. This means if you are HER2 negative, your tumor could become HER2 positive, or if your tumor is HER2 positive, it could become HER2 negative.
How are HER2 positive breast cancers treated?
Once your provider knows that your cancer is HER2 positive, they can use “targeted therapy.” Targeted therapy uses medications that target genes and proteins in cancer cells. This slows down or kills the cancer cells while keeping your healthy cells safe. The targeted therapy medication attaches to HER2 receptors on the surface of breast cancer cells. This blocks the receptors from getting the signals needed to grow. By blocking the signals, the tumor growth can be slowed or stopped.
- There are a few targeted therapies used for the treatment of HER2+ breast cancers.
- They include trastuzumab, pertuzumab, lapatinib, neratinib, ado-trastuzumab emtansine, tucatinib, fam-trastuzumab deruxtecan-nxki, and margetuximab.
- Targeted therapy is often given along with chemotherapy and/or radiation therapy as part of your treatment plan.
- If your cancer is also hormone receptor-positive, you will receive hormone therapy.
- In early-stage breast cancer, you will likely receive the targeted therapy for a certain amount of time. For example, you may be on it for one year.
- In later stage cancer, you may receive targeted therapy for as long as it is working and you can manage the side effects.
How can I manage this diagnosis?
A cancer diagnosis can be challenging. Talk to your team about your treatment options and your goals. Learn about your type of breast cancer and common treatments. This can help you ask questions at your visits and feel more in control of your treatment decisions. Below are resources that can help support you and your loved ones.