Breast Cancer Health Center

Hormone Therapy for Breast Cancer

About two-thirds of women with breast cancer have tumors that contain estrogen receptors (called ER-positive). This type of cancer depends on the female hormone to grow. Hormone therapy is given to block the body's naturally occurring estrogen and fight the cancer's growth. Women who are ER-positive are more likely to respond to hormone treatment than women who are ER-negative.

Tamoxifen for Breast Cancer

Tamoxifen is a pill taken daily and has been used consistently for the past three decades to treat breast cancer. Tamoxifen can be used in women of any age, regardless of whether they've gone through menopause. Long-term (five-year) use of this anti-estrogen drug has been found to reduce the chance of breast cancer recurrence and new breast cancers in women with ER-positive or ER-unknown breast tumors. Doctors also use tamoxifen to treat metastatic breast cancer. 

Women taking tamoxifen are more likely to develop cancer of the uterus (endometrial cancer) than other women. Therefore, they should have regular pelvic exams and tell their doctor about any abnormal uterine bleeding. Other risks include deep-vein thrombosis, blood clots in the lungs, stroke, and cataracts. Minor side effects include hot flashes and mood swings.

Aromatase Inhibitors and Breast Cancer

Aromatase inhibitors are medications that are effective in treating breast cancer, both in early stage and advanced disease, according to new studies. However, they are effective only in women who are past menopause. Aromatase inhibitors, used in both early and advanced breast cancer, prevent estrogen from being produced. They inhibit or inactivate the aromatase enzyme, which is involved in the production of estrogen.

Arimidex (anastrozole), Aromasin (exemestane), and Femara (letrozole) are aromatase inhibitors used to treat estrogen-receptor-positive breast cancer in postmenopausal women, either following tamoxifen treatment or as an initial therapy. 

Side Effects of Aromatase Inhibitors

One serious side effect of aromatase inhibitors is the possible development of osteoporosis or bone fractures. Bone density tests are used to monitor for osteoporosis. 

Other side effects include hot flashes, muscle and joint pain, memory problems, and an increased risk of heart disease.

Ovarian Ablation for Breast Cancer

Studies have shown that some women with breast cancer may benefit from ovarian ablation, if they have not yet gone through menopause and their cancer is estrogen-receptor positive (ER-positive). Ovarian ablation is a procedure that stops the ovaries from producing the estrogen that helps the cancer cells grow. This can be done by:

• Using radiation therapy aimed at the ovaries
• Surgically removing the ovaries
• Giving the woman a luteinizing hormone-releasing hormone (LHRH) agonist. These treatments stop the functioning of the ovaries temporarily.

Ovarian ablation can also be done in combination with tamoxifen therapy. Studies have shown that giving women an LHRH agonist alone or with tamoxifen has been at least as effective as the chemotherapy combination used in hormone-sensitive, early breast cancer and in metastatic breast cancer in premenopausal women.

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