The progress of the women in the trial is still being followed, the researchers noted.
The Womens Health Initiative has also found that women taking estrogen plus another hormone, progestin, had an increased risk both of breast cancer and of benign proliferative breast disease after only about five years of follow-up. This may suggest that progestin plays a role in breast cancer development, the authors stated.
"This makes perfect sense," said Dr. Jay Brooks, chairman of hematology/oncology at Ochsner Health System in Baton Rouge, La. "Estrogen does stimulate breast tissue activity and my concern is that, if you do move along a continuum as the hypothesis states, as you stimulate the breast are you going to be able to predict which women are going to develop into something worse and women who are going to stay in a benign state. I can't predict which of those women will develop [breast cancer] down the line but we know that this agent is highly stimulatory to breast tissue so the question is, do you want to be taking an agent that stimulates breast tissue?"
The U.S. National Heart, Lung, and Blood Institute has more on the Women's Health Initiative.
SOURCES: Tom Rohan, M.D., Ph.D., chairman, department of epidemiology and population health, Albert Einstein College of Medicine, New York City; Jay Brooks, M.D., chairman, hematology/oncology, Ochsner Health System, Baton Rouge, La.; April 8, 2008, Journal of the National Cancer Institute online
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