Estrogen After Hysterectomy Not Linked to Breast Cancer

Women who take estrogen after hysterectomies do not increase their risk of breast cancer, according to new research from a landmark government study.

The findings published today in the Journal of the American Medical Assn. challenge previous research that linked estrogen use to breast cancer, and doctors say women should find comfort in the results.

For years, other data from the same study -- the Women’s Health Initiative -- have uncovered health risks such as increased strokes and blood clots from taking estrogen or another kind of hormone therapy that combines estrogen and progestin.

But doctors said Tuesday that at least for breast cancer and estrogen, the news was good.

“I think this is very reassuring that there is no increased risk of breast cancer,” said Dr. Hugh S. Taylor, director of the Yale Menopause Program and an associate professor at Yale’s medical school. “For women who have had a hysterectomy, it’s becoming a simple decision to take estrogen.”

Doctors say women still need to talk with their doctors to decide whether estrogen is right for them, and a cautious approach to hormone therapy remains the prevailing wisdom. Women who take hormones should use the lowest dose that controls their symptoms, for the shortest time possible -- two to five years.

“This [new study] won’t really change how OB-GYN physicians are counseling their patients,” said Dr. Ashley Hill, a Florida Hospital gynecologist and obstetrician in Orlando. “It used to be that we routinely put women on hormone therapy and left them on it. Now it’s a medicine we only give to women who have symptoms that can’t be treated in other ways, and we’ll continue to do that.”

The breast cancer analysis is the latest research to come from the Women’s Health Initiative, a massive government-backed study that began in the 1990s to look at the health effects of hormones. At the time, doctors widely believed that estrogen and progestin helped women stave off heart disease, dementia and other problems.

Eventually those assumptions were shattered.

Nearly 11,000 women were enrolled in the estrogen portion of the initiative and randomly assigned to either take a daily estrogen pill or a placebo. An additional 16,000 women entered the estrogen-progestin study, where they also were split into two groups of those taking placebos or hormones.

The different approaches are based on the patient’s medical history. A woman who has undergone a hysterectomy -- the removal of her uterus -- takes estrogen alone. Women who still have their uteruses must take estrogen and progestin, because estrogen by itself greatly increases the risk of uterine cancer.

The first surprise came in 2002, when researchers abruptly halted the estrogen-progestin study after discovering a higher rate of breast cancer, heart attacks, strokes and blood clots in women taking the medication.

The estrogen study continued, however, until early 2004, when it also was stopped after scientists noted an increased risk of strokes and blood clots in women taking the hormones. It had no effect on heart disease. Curiously, doctors at that time also found a reduction in breast cancer among those on estrogen but cautioned that the finding needed more analysis.

The new study provides a follow-up examination of breast cancer risk in the 11,000 women in the estrogen research.

To put it into numbers, the data show 34 cases of breast cancer annually per 10,000 women on estrogen versus 42 cases annually per 10,000 women on a placebo. Though there are fewer cases in the estrogen group, the difference is not big enough to indicate any benefit. But it also shows no increased danger with estrogen alone.

“What this means is that we need to stop talking about hormones affecting breast cancer and be very specific, and say estrogen combined with progestin increases breast cancer,” said the study’s lead researcher, Marcia L. Stefanick, a professor of medicine at Stanford University. “Estrogen by itself does not cause breast cancer.”

She added one caveat: The study followed the women for about seven years. The women will continue to be tracked so scientists can see whether a danger emerges later.