RU-486 and breast cancer

New evidence that the abortion pill may help to prevent breast cancer.

Published December 1, 2006 8:41PM (EST)

An exciting health headline today: A UC Irvine study, funded by the National Cancer Institute, the Department of Defense and the Breast Cancer Research Fund, has shown that a sustained dose of RU-486 prevents breast cancer tumors in mice with a genetic predisposition for the disease.

The mice in the study had the gene mutation, shared by about one in 800 women, which leads to uncontrolled cell growth in the mammary glands. According to the National Cancer Institute, around 80 percent of women with the mutation will develop breast cancer.

But fourteen of the mice were implanted with RU-486 pellets which released the drug steadily over a two month period, and none developed breast cancer by their first birthdays. Four mice who received placebo pellets developed tumors by 5.2 months old, while the 25 mice who were untreated had tumors by the time they were 8.7 months old.

RU-486 binds with progesterone receptors, blocking the production of the hormone which is needed for pregnancy. But as a progesterone-blocker, it has long been hoped that the drug might delay or halt the kind of hereditary breast cancer that is believed to be fueled by uncontrolled progesterone production.

Researchers cautioned that at the moment, women won't be able to benefit from long-term doses of RU-486 because in addition to blocking progesterone receptors, it also interferes with other functions like immunity if taken over a long period of time. A more progesterone-specific treatment would be required for humans. Still, this study means great and surprising progress toward that goal.

Eliot Rosen, a Georgetown cancer researcher, told the L.A. Times, "It is a greater effect than I would have expected...It is a little surprising that it completely prevented the tumors."

By Rebecca Traister

Rebecca Traister writes for Salon. She is the author of "Big Girls Don't Cry: The Election that Changed Everything for American Women" (Free Press). Follow @rtraister on Twitter.

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