Endometrial Changes and IUD

2/04 UPDATE: The IUD, marketed as Mirena in Europe by the Germany pharmaceutical company Schering, is now available in the United States.

A new kind of intrauterine device (IUD) appears to prevent the side effects that deter many women from taking the breast cancer drug tamoxifen, British researchers report.

Tamoxifen reduces the chance that breast cancer will recur after treatment. A half-million American women now take the drug, and an estimated 80,000 more will start taking it this year. But the drug is associated with a slight increase in the risk of endometrial cancer -- cancer of the lining of the uterus -- which occurs in about two per 1,000 women each year.

Researchers led by Dr. Francis J. E. Gardner at the University of Leicester report in the Nov. 18 issue of The Lancet that an IUD that releases small amounts of a hormone prevents endometrial changes that could be precursors of cancer.

Gardner and his colleagues tested the new IUD, which releases a hormone called levonorgestrel, in 122 women who had been taking tamoxifen for at least a year. They were looking for polyps, hyperplasia and fibroids, growths that could be early indicators of uterine cancer. Half the women received the IUD; the other half did not. All had the periodic examinations recommended for tamoxifen patients.

"We found no new polyps, no hyperplasia and a 13-percent reduction in fibroids in the women using the IUD," says Gardner, who is a clinical research fellow at Leicester.

At least one earlier study found that injections of progesterone, the active ingredient in the IUD, could have the same effect, he says. "But in order to get a reasonable effect, you must use relatively high doses. This IUD releases progesterone only on the lining of the endometrium. There is minimal systemic absorption, so there are few side effects," Gardner says.

The IUD, marketed as Mirena in Europe by the Germany pharmaceutical company Schering, is now available in the United States. Schering's American subsidiary, Berlex Laboratories, based in Wayne, N.J., has applied for U.S. Food and Drug Administration (FDA) approval.

Mirena is "unique" because it acts by delivering small, steady amounts of levonorgestrel, a progesterone hormone, says Anne King, a spokeswoman for Berlex. The company hopes for FDA approval in the first quarter next year, she says, with the application covering its use as a contraceptive.

Contraception is the only approved use of the IUD in Europe, Gardner says. Its effect on the uterine changes caused by tamoxifen is because the breast cancer drug acts as "a weak estrogen," and he says the progesterone used in Mirena can counteract those effects in the uterus. The major side effect was a temporary increase in vaginal bleeding.

The rule in Britain and other European countries for using the IUD for a purpose other than contraception is the same as in the United States, Gardner says. A physician is free to prescribe it, but "the patient must be aware that the device is not currently licensed for this use."

Ultimately, the journal report says, "to make a case for routine use of the device in the thousands of women prescribed tamoxifen each year, there is a need for a large randomized controlled trial to include the insertion of the device for the duration of tamoxifen treatment."

What To Do

Keep your antennae up. If you are taking tamoxifen after breast cancer therapy, ask your physicians about the availability of the IUD, and whether it might be suitable for you.

The National Cancer Institute has information on breast cancer, including a Q&A on the benefits and risks of tamoxifen.

SOURCES: Interviews with Francis J. E. Gardner, M.D., professor, department of obstetrics and gynecology, University of Leicester, Leicester, England; Anne King, spokeswoman, Berlex Laboratories, Wayne, N.J.; By Edward Edelson HealthScout Reporter

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