Long use of estrogen linked to breast cancer

Large study finds danger increases sharply after 15 years


Women who take an estrogen hormone supplement longer than 15 years are at a significantly increased risk of developing breast cancer, according to a long-term study of nurses' health published yesterday.

But the research, reported in the Archives of Internal Medicine, found no increased risk of breast cancer in women who had taken estrogen for less than 10 years.

Researchers said the findings should be reassuring for women who want to use estrogen for a short time to relieve menopausal symptoms such as hot flashes and vaginal dryness.

"This says, at least for the shorter-term users, you don't need to panic," said Dr. Wendy Chen, an oncologist and epidemiologist at Brigham and Women's Hospital and the Dana-Farber Cancer Institute in Boston, who led the study. "But for the longer-term users, you need to think about why am I still taking estrogen for this long of time, and are there are alternatives?"

Last month, researchers in another long-term study, the Women's Health Initiative, published results of a seven-year study that found no increased risk of breast cancer in women who took the hormone, but there were other significant health risks, such as strokes and blood clots.

Estrogen-alone supplements are given only to women who have had their uteruses removed, because the hormone has been linked to an increased risk of uterine cancer. A woman with an intact uterus can take estrogen combined with progestin, another hormone that seems to prevent women from getting uterine cancer.

The latest study involved more than 28,000 women who were part of the Nurses' Health Study conducted by researchers at two Harvard-affiliated hospitals in Massachusetts.

For women who had been on estrogen for at least 15 years, the risk of hormone-responsive breast cancer - the most common type in the United States - climbed 48 percent. At 20 years, the risk of all types of breast cancer rose 42 percent.

Of the 934 invasive breast cancers that developed over the duration of the study, 708 were in women taking estrogen at the time, the study showed. Among the women who never used hormones, 226 developed breast cancer.

The risk of breast cancer also appeared to rise between 10 and 15 years of use, but the increase was not statistically significant, the researchers said.

Before the Women's Health Initiative, doctors routinely prescribed hormone supplements at menopause. The prevailing theory was that estrogen or estrogen with progestin would prevent heart disease and other vagaries of aging. Instead, the study found an increased risk of heart disease, dementia, stroke, blood clots and other serious illnesses. More than 161,000 women participated.

Dr. Carolyn D. Runowicz, president of the American Cancer Society, said a few women in her practice have chosen to remain on estrogen for a long time because they feel the improvement in their quality of life outweighs the risks.

Runowicz called the study reassuring for short-term estrogen use but also said it underscores the need for patients to regularly "justify every medication" they take with their doctors.

"Is it estrogen forever? That's what we thought in the 1970s," said Runowicz, director of the Cancer Center at the University of Connecticut Health Center, "but we've completely reversed our thinking on that."

Wyeth, which produces the estrogen pill Premarin, considers the Nurse's Health Study a well-respected study and the most recent research a "fairly reasonable trial," said Dr. James Pickar, assistant vice president for clinical research and development.

Pickar said he sees the results as good news for women because they back up the WHI findings that found no increased breast cancer risk for short-term estrogen users.

Nancy McVicar writes for the South Florida Sun-Sentinel. The Associated Press contributed to this article.

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