When your doctor talks with you about treatment options for breast cancer, they might suggest hormone therapy. Only patients with hormone-receptor-positive breast cancer (HR+) will be prescribed hormone therapy — but most breast cancers fall into this category. Hormone therapy can be used in addition to surgery, chemotherapy, and radiation, and your doctor will develop a treatment plan tailored to your specific needs.
Hormones are chemical messengers in the body that trigger changes in various cells and tissues. The two hormones that affect breast cancer are estrogen and progesterone.
Normally, estrogen contributes to the growth and development of female sex characteristics as well as the growth of long bones; and normally progesterone is responsible for aspects of a woman’s menstrual cycle and pregnancies.
But these hormones can sometimes also fuel cancer cell growth
If you have HR+ breast cancer, it means the cancer cells in your body have special proteins called hormone receptors that bind to the hormones estrogen and/or progesterone. Once binded, these hormones spur the cancer’s growth.
HR+ breast cancer is very common. It is more likely that your cancer will be fueled by estrogen, or estrogen and progesterone together, than progesterone alone. About 80% of breast cancers are estrogen-receptor positive (ER+), and 65% are ER+ and progesterone-receptor-positive (PR+). Only about 2% of breast cancers are ER- but PR+.
Hormone therapy works by blocking your HR+ cancer cells from receiving estrogen or progesterone, and this is done in several different ways. It may be given before, during, or after other cancer treatments; it can be given to premenopausal or postmenopausal women; it can be used on terminal patients or patients with any stage of breast cancer; and it can be given to reduce the risk of breast cancer if you’re high risk but don’t yet have the disease, and can also be given to reduce the risk of recurrence.
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Identifying hormone receptors
Your doctor will test the tissue removed from your tumor during a biopsy. If it has receptors for estrogen (ER+), progesterone (PR+), or both, it is hormone-receptor-positive; if it lacks receptors for both, it is considered hormone-receptor-negative (ER- and PR-). If negative, hormone therapy will not be a treatment option.
The HER-2/neu gene is also responsible for the growth of some tumors, and there are specific therapies for that as well. When your cancer lacks receptors for estrogen, progesterone, and the HER-2/neu protein, it is called triple negative breast cancer (TNBC), and it is a very aggressive form of the disease. Learn more about that here.
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