Hormone therapy is another form of systemic therapy. Like chemotherapy, hormone therapy can be used either as an adjuvant therapy to help reduce the risk of cancer recurrence after surgery or when the cancer has become metastatic.

Some breast cancers grow in response to the hormone estrogen. Estrogen is usually thought of as a "female" hormone, but men have it in their bodies as well, just at lower levels. About 9 out of 10 breast cancers in men have hormone receptors on the surface of their cells -- that is, their cancers are estrogen receptor (ER)-positive and/or progesterone receptor (PR)-positive. This makes them more likely to respond to hormone treatments. Hormone therapy does not help patients whose tumors are both ER- and PR-negative.

Several approaches to blocking the effects of estrogen or lowering estrogen levels are used to treat breast cancer in women. While many of these may work in men as well, doctors have the most experience with using anti-estrogen drugs such as tamoxifen in men.

In the metastatic setting, hormonal treatments are often used in a sequence. For example, tamoxifen may be tried first. If the cancer does not respond or if it grows back after an initial response, other hormonal treatments may be tried.

Tamoxifen: Tamoxifen works by blocking the estrogen receptors on cancer cells, which prevents estrogen from spurring their growth. It is taken daily in pill form, usually for 5 years, to reduce the chances of the cancer coming back after surgery. Tamoxifen can also be used to treat advanced breast cancer.

The most common side effects include fatigue, hot flashes, and sexual problems. A rare but more serious side effect is blood clots, which usually form in deep veins of the leg. In some cases, this increased risk of clotting may lead to a heart attack, stroke, or blood clots spreading to the lungs (pulmonary embolism). Call your doctor or nurse right away if you develop pain, redness, or swelling in your lower leg (calf), shortness of breath, chest pain, sudden severe headache, confusion, or trouble speaking or moving.

Aromatase inhibitors: This group of drugs includes anastrozole (Arimidex), letrozole (Femara), and exemestane (Aromasin). They block the production of small amounts of estrogen by the adrenal glands. They are taken daily as pills. They have been found to be very effective in treating breast cancer in women, but they have not been well studied in men. Still, some doctors use them as the first line of hormone therapy instead of tamoxifen. Clinical trials are also under way to look at using aromatase inhibitors along with LHRH analogs (see below).

The main side effects of these drugs are thinning of the bones and joint stiffness.

Megestrol: Megestrol (Megace) is a progesterone-like drug. It is unclear how it stops cancer cells from growing, but it appears to compete for hormone receptor sites in the cells. This is an older drug that is usually reserved for men who are no longer responding to other forms of hormone therapy. Megestrol may increase the risk for blood clots and frequently causes weight gain through an increase in appetite.

Orchiectomy (castration): Surgical removal of the testicles greatly lowers the levels of testosterone and other androgens (male hormones) in the body. Most male breast cancers contain androgen receptors that may cause the cells to grow. Androgens can also be converted into estrogens in the body. Orchiectomy shrinks most male breast cancers, and may help other treatments like tamoxifen become more likely to work. This treatment was once quite common, but it is now used less often because of new non-surgical approaches to lowering androgen levels, such as those below.

Luteinizing hormone-releasing hormone (LHRH) analogs and anti-androgens: LHRH analogs such as leuprolide (Lupron) and goserelin (Zoladex) affect the pituitary gland and, indirectly, cause the testicles to lower their production of androgens. They are given as shots either monthly or every few months. Anti-androgens such as flutamide and bicalutamide work by blocking the effect of male hormones on breast cancer cells. These drugs are taken as daily pills. LHRH analogs, either alone or with anti-androgens, are often effective in shrinking male breast cancers. Doctors are also studying the use of LHRH analogs along with aromatase inhibitors.

Possible side effects of hormone therapy

While some of these drugs have unique side effects (see descriptions above), in general they can cause loss of sexual desire, trouble having an erection, weight gain, hot flashes, and mood swings. Be sure to discuss any such side effects with your cancer care team because there may be ways to treat them.

Last Medical Review: 09/24/2008
Last Revised: 05/13/2009