What is HR+ and HER2- Breast Cancer?
Receiving a breast cancer diagnosis can be overwhelming. Not only is it an emotional experience, you're also likely to receive a lot of information all at once. Trying to understand the explanation of your diagnosis (and the medical jargon that comes along with it) may feel like learning a foreign language, but by breaking down the diagnosis and treatment process, you’ll soon become fluent.
The First Step: Determining Your Breast Cancer Type
To choose the best treatment, your doctor needs to identify key factors about your specific type of breast cancer. A number of important tests will be performed in the beginning to accomplish this. Some will be used to determine the size of the tumor and whether the cancer has spread to your lymph nodes or other parts of your body. Based on these test results, your cancer will be given a stage from I to IV.
Other tests look at the cancer cells themselves. Under a microscope, tumor cells are studied to check for the presence of proteins called hormone receptors (HR) and human epidermal growth factor receptor 2 (HER2). This helps your doctor understand how your cancer cells grow and therefore provides a road map for how to fight them. If your cancer cells do have hormone receptors, your cancer is considered hormone receptor-positive (HR+); if few or no hormone receptors are seen, it is considered hormone receptor-negative (HR-) If you have an excess number of HER2 receptors, your cancer is considered HER2-positive (HER2+); conversely, if few or no HER2 receptors are found, your cancer will be called HER2-negative (HER2-).
The most common type of breast cancer is HR+/HER2-. About 70% of all breast cancers fall into this category.
Understanding the Role of Hormone Receptors and HER2
Hormone receptors respond to the reproductive hormones, estrogen and progesterone. When these hormones attach to the cancer cells, they signal the cancer cell to grow. If your cancer is HR+, your doctor may indicate which specific hormone receptors are present: estrogen receptor-positive (ER+), progesterone receptor-positive (PR+), or both (ER+/PR+).
HER2 protein receptors are found on all breast cells; they play a role in how breast cells grow. However, some breast cancer cells have too many HER2 receptors, making the cells divide too rapidly. As a result, this type of cancer can grow and spread quickly. Around 25% of breast cancers are HER2+.
Treating HR+/HER2- Breast Cancer
If you have HR+/HER2- breast cancer, you will likely first receive some traditional forms of cancer treatment: surgery, chemotherapy, and radiation. Surgery is performed to try and remove the cancer, either by removing the tumor, the whole breast, and/or any affected lymph nodes. Strong beams of radiation may be directed at the affected area in an attempt to kill the cancer cells. Powerful chemotherapy drugs may be given to destroy the cancer cells and try and prevent it from returning.
Additionally, due to the presence of hormone receptors, a special kind of treatment known as hormone therapy may be used to keep the cancer from growing or spreading. These drugs block the hormones from attaching to the receptors on the cancer cells; they can also decrease the amount of estrogen in the body. Some common forms of hormone therapy include the following:
Selective estrogen receptor modulators (SERMs): the most frequently used SERM is called tamoxifen (Soltamox, Nolvadex). These drugs prevent estrogen from acting on the cancer cells.
Luteinizing hormone-releasing hormone (LHRH) analogs: drugs such as goserelin (Zoladex) and leuprolide (Lupron) are used in pre-menopausal women to stop their ovaries from producing estrogen. Some women have surgery to remove their ovaries completely.
Aromatase inhibitors: medications such as anastrozole (Arimidex), letrozole (Femara) and exemestane (Aromasin) are used in post-menopausal women. They stop estrogen from being produced in areas of body other than the ovaries.
Certain types of targeted therapy may also be used for HR+/HER2- breast cancer, especially when the cancer metastasizes. This form of treatment attacks the cancer cells, but leaves normal cells alone. Some targeted therapies improve the effectiveness of chemotherapy and hormone therapy.
CDK4/6 inhibitors: these drugs target the cyclin-dependent kinase (CDK) proteins within the cell. This stops breast cancer cells from dividing. Palbociclib (Ibrance) and ribociclib (Kisqali) are two examples.
Everolimus (Afinitor): this targeted therapy is used for post-menopausal women and blocks a protein known as mTOR. This makes it hard for the breast cancer cells to grow and divide. It may also stop the tumor from creating new blood vessels.
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