Hormone therapy for endometrial cancer

Hormone therapy is the use of hormones or hormone blocking drugs to fight cancer. This type of hormone therapy is not the same as hormones given to treat the symptoms of menopause (menopausal hormone therapy).

Progestins

The main hormone treatment for endometrial cancer uses progesterone-like drugs called progestins. The 2 most commonly used progestins are medroxyprogesterone acetate (Provera^®, which can be given as an injection or as a pill) and megestrol acetate (Megace^®, which is given as a pill). These drugs work by slowing the growth of endometrial cancer cells. Side effects can include increased blood sugar levels in patients with diabetes. Hot flashes, night sweats, and weight gain (from fluid retention and an increased appetite) also occur. Rarely, serious blood clots are seen in patients on progestins.

Sometimes endometrial hyperplasia and early endometrial cancers can be treated with an intrauterine device that contains levonorgestrel, a progestin. This may be combined with another hormone drug, such as medroxyprogesterone acetate or a gonadotropin-releasing hormone agonist (see below).

Tamoxifen

Tamoxifen, an anti-estrogen drug often used to treat breast cancer, may also be used to treat advanced or recurrent endometrial cancer. The goal of tamoxifen therapy is to prevent any estrogens circulating in the woman's body from stimulating growth of the cancer cells. Even though tamoxifen may prevent estrogen from nourishing the cancer cells, it acts like a weak estrogen in other areas of the body. It does not cause bone loss, but it can cause hot flashes and vaginal dryness. People taking tamoxifen also have an increased risk of serious blood clots in the leg.

Gonadotropin-releasing hormone agonists

Most women with endometrial cancer have had their ovaries removed as a part of treatment. In others, radiation treatments have made their ovaries inactive. This reduces the production of estrogen and may also slow the growth of the cancer. Gonadotropin-releasing hormone (GNRH) agonists are another way to lower estrogen levels in women with functioning ovaries. These drugs switch off estrogen production by the ovaries in women who are premenopausal. Examples of GNRH agonists include goserelin (Zoladex^®) and leuprolide (Lupron^®). These drugs are injected every 1 to 3 months. Side effects can include any of the symptoms of menopause, such as hot flashes and vaginal dryness. If they are taken for a long time (years), these drugs can weaken bones (sometimes leading to osteoporosis).

Aromatase inhibitors

After the ovaries are removed (or are not functioning), estrogen is still made in fat tissue. This becomes the body's main source of estrogen. Drugs called aromatase inhibitors can stop this estrogen from being formed and lower estrogen levels even further. Examples of aromatase inhibitors include letrozole (Femara^®), anastrozole (Arimidex^®), and exemestane (Aromasin^®). These drugs are most often used to treat breast cancer, but may be helpful in the treatment of endometrial cancer. Side effects can include joint and muscle pain as well as hot flashes. If they are taken for a long time (years), these drugs can weaken bones (sometimes leading to osteoporosis). These drugs are still being studied for use in treating endometrial cancer.