Hormonal therapy, sometimes also called anti-estrogen therapy, works by lowering the amount of estrogen in the body or blocking estrogen from attaching to the breast cancer cells.
You and your doctor will work together to decide which form of hormonal therapy is best in your situation. Topics you may discuss include: other features of the breast cancer, such as stage; other medical conditions you may have; whether or not you have been through menopause (menstrual periods have stopped); and your personal preferences.
The main types of hormonal therapy that may be used include:
- Selective estrogen-receptor response modulators (SERMs). SERMs block the effects of estrogen in the breast tissue by attaching to the estrogen receptors in breast cells. Tamoxifen is the SERM most commonly used to treat breast cancer. Another SERM called Fareston (chemical name: toremifene) is sometimes used to treat advanced breast cancer in postmenopausal women.
- Aromatase inhibitors. Aromatase inhibitors stop the production of estrogen in postmenopausal women. Aromatase inhibitors work by blocking the enzyme aromatase, which turns the hormone androgen into small amounts of estrogen in the body. This means that less estrogen is available to stimulate the growth of hormone-receptor-positive breast cancer cells. Aromatase inhibitors can't stop the ovaries from making estrogen, so these medications only work in postmenopausal women. The main sources of the hormone for those women are the adrenal glands and fat tissue, not the ovaries. Aromatase inhibitors include Arimidex (chemical name: anastrozole), Aromasin (chemical name: exemestane), and Femara (chemical name: letrozole).
- Estrogen-receptor downregulators (ERDs). Estrogen receptor downregulators, called ERDs for short, block the effects of estrogen in breast tissue. ERDs sit in the estrogen receptors in breast cells. If an ERD is in the estrogen receptor, there is no room for estrogen and it can't attach to the cell. ERDs also reduce the number of estrogen receptors and change the shape of breast cell estrogen receptors so they don't work as well. Faslodex (chemical name: fulvestrant) is an ERD that may be used alone as the first treatment for postmenopausal women diagnosed with hormone-receptor-positive, HER2-negative, advanced-stage breast cancer that hasn’t been treated with hormonal therapy. Faslodex also may be used to treat advanced-stage, hormone-receptor-positive breast cancer in postmenopausal women if other hormonal therapy medicines, such as tamoxifen, are no longer working.
- Luteinizing hormone-releasing hormone agents (LHRHs). LHRHs shut down the ovaries and stop them from producing estrogen, which means less estrogen is available to help support the growth of hormone-receptor-positive breast cancer. LHRHs are usually given by injection once a month for several months, or every few months. Premenopausal women with early-stage, hormone-receptor-positive breast cancer can be treated with LHRHs. Examples include Zoladex (chemical name: goserelin), Lupron (chemical name: leuprolide), and Trelstar (chemical name: Triptorelin). When the medicine is stopped, the ovaries begin functioning again. The time it takes for the ovaries to recover can vary from woman to woman.
Other hormonal therapies may be used to treat advanced breast cancer that is hormone-receptor-positive and does not respond to the treatments listed above. Megace (chemical name: megestrol) is a form of progestin that suppresses the effects of estrogen on breast cancer cells. Halotestin (chemical name: fluoxymesterone) is an anabolic steroid that lowers the amount of estrogen in the body.
Prophylactic ovary removal is another, more aggressive way some premenopausal women may choose to significantly lower the amount of estrogen in the body. This is a serious surgery that can have a considerable impact on a woman’s life. Learn more about prophylactic ovary removal.
For more information on all of these treatments, visit the Hormonal Therapy section.