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Breast Cancer Health Center

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New Answer for Tamoxifen Problem

WebMD Health News

Nov. 16, 2000 -- A birth control device is being tested as a way to protect women from dangerous side effects associated with a common breast cancer drug.

Tamoxifen is one of the most effective and widely used medications doctors can give women battling breast cancer. In studies, tamoxifen has been shown to help prevent recurrences of breast cancer when taken for five years after surgery. It also is being researched as a way of preventing breast cancer in women at high risk for the disease.

Tamoxifen can cause vaginal bleeding and stimulate growths in the endometrium, the lining of the uterus. The new findings are important because changes in the uterus -- though not always serious -- are fairly common among women taking tamoxifen to treat breast cancer.

"A third of women [taking tamoxifen] will develop either polyps or endometrial [growths] over five years, and there is approximately a three-times increased risk of endometrial cancer," says Francis Gardner, MD, of the University of Leicester in the U.K.

In a study of 113 postmenopausal women who had taken tamoxifen for at least one year, Gardner randomly fitted about half of them with an IUD, a birth control device placed in the uterus. The remaining women did not receive an IUD, but all 113 women received special exams over a one-year period to check for changes in the endometrium. The study appears in Friday's issue of The Lancet.

After one year, women who had the IUD had no new growths and 13% fewer fibroids than women who did not get the IUD, according to Gardner. Also, those who had the IUD showed no change in the uterus.

The IUD releases small amounts of the hormone levonorgestrel every day. Like other IUD's, the one used in the study is intended for birth control, but the researchers theorize that levonorgestrel, which is a progestagen, may protect the lining of the uterus from overgrowing in response to tamoxifen.

One expert says the approach makes sense, but he questions whether all women who take tamoxifen should be using the IUD to protect against endometrial changes. Patrick Neven, MD, suggests that the IUD may only be justified for women who already have had such changes.

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