Hormone therapy. Hormone therapy is used to prevent the growth, spread, and recurrence of breast cancer. The female hormone called estrogen can increase the growth of breast cancer cells in some women. Hormones are chemicals produced by glands, such as the ovaries and testicles. Hormones help some types of cancer cells to grow, such as certain breast cancers and prostate cancer. Hormone therapy may be considered for women whose breast cancers test positive for estrogen or progesterone receptors.
A hormone receptor test measures the amount of certain proteins (called hormone receptors) in cancer tissue. Hormones (such as estrogen and progesterone that naturally occur in the body) can attach to these proteins. If the test is positive, it indicates that the hormone is probably helping the cancer cells to grow. In this case, hormone therapy may be given to block the way the hormone works and/or help keep the hormone from attaching to the receptors on the cancer cells. If the test is negative, the hormone does not affect the growth of the cancer cells, and other cancer treatments are given.
Always discuss the results of the hormone receptor test with your doctor.
An anti-estrogen drug frequently used, called tamoxifen, blocks the effects of estrogen on the growth of cancer cells in breast tissue. However, tamoxifen does not stop the production of estrogen. Side effects that may occur when taking tamoxifen include hot flashes, nausea or vomiting, vaginal spotting, fatigue, headaches, and skin rash.
Taking tamoxifen also increases the risk of endometrial cancer (cancer of the lining of the uterus) and uterine sarcoma (cancer involving the muscular wall of the uterus). There is also a small risk of blood clots and stroke.
Raloxifene, a second anti-estrogen drug used for breast cancer prevention, is not recommended for women who have already been diagnosed with breast cancer.
Drugs called aromatase inhibitors are used to prevent the recurrence of breast cancer in postmenopausal women. These drugs, anastrozole (Arimidex), exemestane (Aromasin), and letrozole (Femara), prevent estrogen production. Possible side effects of these drugs include osteoporosis or bone fractures.
Another drug for recurrent breast cancer is fulvestrant (Faslodex). Also approved by the FDA, this drug eliminates the estrogen receptor rather than blocking it, as is the case with tamoxifen, letrozole, exemestane, or anastrozole. This drug is used following previous anti-estrogen therapy. Side effects for fulvestrant include hot flashes, mild nausea, and fatigue.
Another means of stopping the production of estrogen is the use of surgery to remove the ovaries in women who have not gone through menopause. This surgery is called an oophorectomy and it eliminates the main source of estrogen.