Big news yesterday out of Boston: Pharmaceutical giant Eli Lilly has settled a case brought against it by four sisters who developed breast cancer in their forties, decades after their mother took the synthetic estrogen DES (Diethylstilbesterol) during her pregnancies. A total of 51 women have filed lawsuits in Boston against more than a dozen companies that made or marketed DES, and this was the first case to go to trial. The settlement was announced Wednesday on the second day of testimony.
This is the latest chapter in the tragic legacy of DES. Between 1938 and 1971, doctors prescribed DES for millions of pregnant women to prevent miscarriages – without having been tested for its effect on fetuses. It is now clear that not only was DES ineffective for preventing miscarriages but it had devastating effects on those exposed in the womb. The drug was banned when daughters of women who took the drug were found to have higher rates of an extremely rare vaginal cancer when compared to the daughters of women who did not take the drug. Later, evidence emerged that DES exposure is also associated with an increased risk of breast cancer in the women who took it during the 1950s.
In a follow-up study of daughters who were exposed prenatally to DES, a nearly twofold increase in breast cancer risk was observed in women older than age 40. An even greater effect was found for women over the age of 50, although relatively few of the daughters had yet reached that age at the time of the study. Women exposed in utero who had the most severe abnormalities of their vaginal epithelial cells (an indicator of exposures to higher doses of DES) also had a higher risk for developing breast cancer. The evidence about the health consequences of DES was one of the first indicators that exposure to endocrine-disrupting compounds in the womb can increase risk for later life breast cancer.
The story of DES should serve as a cautionary tale. This tale underscores the need for chemicals testing protocols that consider the risks of exposures early in life. We need chemical testing that looks at the effects of chemicals across the lifespan and that measures early signs for concern – such as exposure-induced changes to how the mammary gland develops – if we are going to prevent such tragic events in the future. And this evidence needs to be folded into comprehensive chemicals policies that ensure these kinds of exposures do not occur as the result of prescribed pharmaceuticals or from inadvertent exposure to chemicals used for other purposes.