Women using estrogen after menopause run a slightly greater risk of breast cancer, according to a study of more than 118,000 nurses. But the authors of the study, which appeared last week in the Journal of the American Medical Assn., emphasized that the increased risk was modest and noted that estrogen therapy holds many benefits for post-menopausal women.
“While this study adds to a large body of information, I would not recommend that a woman change her current use of estrogen therapy based on these data alone,” said one of the authors, Dr. Meir Stampfer, of the Harvard School of Public Health in Boston.
The researchers, led by Graham Colditz of Boston’s Brigham and Women’s Hospital, also said the additional risk of breast cancer dropped a year after the women stopped taking the female sex hormones. Taking estrogen after menopause can help prevent calcium loss from bones and may help prevent heart disease, the leading killer of older women.
Even so, “these data suggest the need for caution in the use of estrogens,” the authors wrote.
Researchers found the post-menopausal women taking estrogen were 35% to 40% more likely to develop breast cancer than those who did not take the hormone. But the risk was only about half that a woman might face if her mother had breast cancer, researchers said.