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Preeclampsia May Have Breast Cancer Benefits

Women who have suffered multiple bouts of preeclampsia – a complication of pregnancy characterized by high blood pressure – can look forward to a surprising benefit of the disease: a much reduced risk of breast cancer.
   A new study by CUMC researchers shows that women who experienced two or more bouts of preeclampsia have a 70 percent lower risk of developing breast cancer than women with uncomplicated pregnancies.
   Women who had one pregnancy complicated by preeclampsia also benefit, the study shows, but not as dramatically. They are 30 percent less likely to develop breast cancer. The study is the first to show that breast cancer risk declines as the number of preeclampsic pregnancies goes up.
   “The stronger association by number of events helps us understand how preeclampsia may influence breast cancer,” says the study’s lead author, Mary Beth Terry, Ph.D., associate professor of epidemiology at the Mailman School. “Preeclampsic pregnancies have a different hormonal profile, which may have an cumulative effect on breast cancer risk.”
   Other studies have reported that women with preeclampsia have lower levels of estrogen and
certain growth factors and higher levels of androgens, alpha-fetoprotein, and human chorionic gonadotropin. This hormonal profile may be favorable in terms of breast cancer risk.
   The new study, published in the American Journal of Epidemiology, is also the first to report that the protection from breast cancer associated with preeclampsia extends to post-menopausal women and is in fact strongest in these women. Previous studies primarily looked at breast cancer in younger women.
   Dr. Terry says it is possible that epidemiological studies of preeclampsia and breast cancer may point to new ways to prevent or treat breast cancer in the future, but the study was mainly designed to shed more light on how pregnancy affects breast cancer.
   Women have a higher risk of breast cancer in the first few years after pregnancy, but have a lower long-term risk. Researchers hypothesize that a surge of hormones during pregnancy increases short-term risk by fueling the growth of pre-existing tumors. The surge, at the same time, is believed to decrease long-term risk by increasing the differentiation of cells in the breast.

The research was supported by the NIH.