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Long-term estrogen therapy may be related to a higher risk of breast cancer among post-menopausal women.
That new analysis, published in the current issue of the Archives of Internal Medicine, comes from a study of thousands of nurses who used hormones to treat the symptoms of menopause.
NPR's Allison Aubrey reports.
ALLISON AUBREY reporting:
Estrogen therapy makes it into headlines more than most health issues. Usually the message is that researchers have found more reasons to limit the use of hormones. The results of huge clinical trials of tens of thousands of women, released two years ago, showed that a combination of estrogen and progestin therapies increased the risk of heart problems, blood clots, and breast cancer.
Gail Greendale, a professor of medicine at UCLA, describes the reaction to those findings as…
Dr. GAIL GREENDALE (research director of the Iris Cantor-UCLA Women's Health Center): Really wholesale fear and panic on the part of both physicians and women, with women stopping their hormones abruptly.
AUBREY: But in recent months, the message has become more nuanced as researchers learn more about how the risks of hormone therapy can accumulate.
Last month, an analysis of the Women's Health Initiative trial, found that women who took estrogen for seven years or less, following a hysterectomy, did not have higher rates of breast cancer - encouraging to short-term estrogen users.
Now, researchers at Dana-Farber Cancer Institute in Boston, are reporting what they've learned about long-term use. And the picture is quite different.
Dr. WENDY CHEN (Dana-Farber Cancer Institute, Boston): So what we found is that, if you looked at all types of breast cancer, there was a statistically significant increased risk of breast cancer for women who had used continuous estrogen for 20 or more years.
AUBREY: Meaning women who took estrogen only, without progestin, longer than a decade, did face an increased risk of breast cancer. Wendy Chen, of Dana- Farber, says they were one had a half times more likely to develop breast cancer than women who never took hormones.
JoAnn Manson is Chief of Preventive Medicine at Brigham and Women's Hospital in Boston and another author of the study. She says the kinds of cancers that showed up earliest among the long-term estrogen users where the hormone positive types.
Dr. JOANN MANSON (Chief, Preventative Medicine, Brigham and Women's Hospital, Boston): It suggests that the estrogen and progesterone receptor positive tumors may be more sensitive to stimulation by estrogen therapy use.
AUBREY: Something researchers had hypothesized.
Manson says, this latest analysis may help women who've struggled over the decision to use hormones temporarily after a hysterectomy.
Dr. MANSON: The findings are reassuring for women using estrogen alone, without a progestin, for less than 10-years duration. And many women who are using estrogen for treatment of hot flashes or other menopausal symptoms, will use hormone therapy only short-term, or less than ten years.
AUBREY: UCLA's Gail Greendale says the findings will help further refine her recommendations to patients.
Dr. GREENDALE: What this analysis allows us to do is to give women a little bit more information about what the window of safe time, if you will, with respect to breast cancer, is.
AUBREY: For women concerned about blood clots or strokes, the 10-year window may not be safe. For this reason, Greendale says the broader message remains: hormone therapy should be used in the smallest possible dose, for the shortest period of time, needed to treat symptoms.
Allison Aubrey, NPR News, Washington. Transcript provided by NPR, Copyright NPR.
