Breast Cancer Current Topics in Breast Cancer

“DES Daughters” at Risk for Breast Cancer

Daughters of women who took the drug diethylstilbestrol (DES) during pregnancy may be at a greater risk for breast cancer, say researchers from the Boston University School of Public Health.

DES was commonly prescribed for over 40 years to prevent miscarriage, but prescription of the drug stopped after research showed that women taking DES had a higher risk of breast cancer. Additionally, their daughters were more likely to develop a type of vaginal and cervical cancer and have difficulty getting pregnant or delivering a healthy baby.

But as the daughters exposed to DES begin to enter menopause, the time when breast cancer risk is higher for all women, researchers have found that on top of all of these other risks, DES daughters also have a greater risk of developing breast cancer.

“This is really unwelcome news because so many women worldwide were prenatally exposed to DES, and these women are just now approaching the age at which breast cancer becomes more common,” said Dr. Julie Palmer, lead study author and professor of epidemiology at the Boston University School of Public Health.

In the early 1900s, scientists believed that low estrogen levels caused pregnant women to either have a miscarriage or deliver early. To combat this, DES, a synthetic estrogen, was developed and given to as many as 10 million pregnant women. Even though research in 1950 showed that DES did not lower the risk of having a miscarriage, it was still prescribed through 1971 until the FDA banned the use of the drug.

For the study, published in Cancer Epidemiology, Biomarkers & Prevention, Palmer looked at almost 5,000 women who had been exposed to DES in the womb and 2,000 women who were not exposed. Among the DES daughters, 76 reported being diagnosed with breast cancer, while only 26 of the unexposed women developed the disease.

Ultimately, women over the age of 40 who were exposed to DES in the womb have twice the risk of developing cancer as the rest of the population, the researchers concluded. Additionally, it seems that DES daughters over the age of 50 have an even higher risk of developing breast cancer, but more work needs to be done to determine the severity of that risk.

Regardless of individual risk, Palmer and colleagues urge all women exposed to DES to tell their doctors and have annual mammograms to screen for breast cancer. And since hormonal supplements for menopause only increase one’s risk of breast cancer even more, DES daughters should think twice before taking them.

“It might be wise for exposed women to avoid such supplements,” said Palmer.