Hormonal Therapy

Hormone therapy is another form of adjuvant systemic therapy. The hormone estrogen is produced mainly by a woman's ovaries until menopause. After menopause it is made mostly in the body’s fat tissue, where a testosterone-like hormone made by the adrenal gland is converted into estrogen. Estrogen promotes the growth of about two thirds of breast cancers (those containing estrogen or progesterone receptors and called hormone receptor positive cancers). Because of this, several approaches to blocking the effect of estrogen or lowering estrogen levels are used to treat breast cancer.

Tamoxifen: The antiestrogen drug that has been used most often is tamoxifen (Nolvadex). It is taken daily in pill form. Taking tamoxifen after surgery, usually for 5 years, reduces the chances of the cancer coming back by about 50% for women with early breast cancer, if the cancer contained estrogen or progesterone receptors. Tamoxifen is also used to treat metastatic breast cancer and to prevent the development of breast cancer in a woman at high risk.

Toremifene: Toremifene (Fareston), another anti-estrogen drug closely related to tamoxifen, may be an option for postmenopausal women with breast cancer that has metastasized. Toremifene is an anti-estrogen medicine that is used in tumors that are estrogen-receptor positive or whose estrogen-receptor status is unknown.

Fulvestrant: Fulvestrant (Faslodex) is a newly approved drug that also acts via the estrogen receptor, but instead of blocking it, this drug eliminates it. It is often effective even if the breast cancer is no longer responding to tamoxifen. It is given by injection once a month. Hot flashes, mild nausea, and fatigue are the major side effects. It is only given to women who are already in menopause. It is currently only approved for use in women with advanced breast cancer.

Aromatase inhibitors: Three drugs that stop estrogen production in postmenopausal women have been approved for use in treating both early and advanced breast cancer. These drugs are letrozole (Femara), anastrozole (Arimidex), and exemestane (Aromasin). They work by blocking an enzyme responsible for producing small amounts of estrogen in postmenopausal women. They cannot stop the ovaries of premenopausal women from producing estrogen. For this reason they are only effective in postmenopausal women.

Ovarian ablation: Removing estrogens from premenopausal women is another effective way of treating breast cancer in hormone-responsive cancer. This can be done surgically, by removing the ovaries. It also can be done with drugs called luteinizing hormone-releasing hormone (LHRH) analogs. The usual drugs are goserelin (Zoladex) or leuprolide (Lupron). These drugs block the mechanism that causes ovaries to make estrogens. They are now being tested as adjuvant therapies. Chemotherapy drugs may also damage the ovaries of premenopausal women so they no longer produce estrogen.

Megestrol acetate: Megestrol acetate (Megace) is a progesterone-like drug used for hormone treatment of advanced breast cancer, usually for women whose cancers do not respond to the other hormone treatments. Its major side effect is weight gain, and it is sometimes used to reverse weight loss in patients with advanced cancer.

Other ways to control hormones: Androgens (male hormones) may be considered after other hormone treatments for advanced breast cancer have been tried. Androgens cause masculine characteristics to occur, for example, more body hair and a deeper voice. They are sometimes effective.