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DES, a drug given to women 40 years ago to help prevent miscarriages, may increase the
risk of breast cancer in those women’s daughters. According to preliminary results of
a long-term study, exposure to DES while in the womb increased risk of breast cancer in
women over 40 years of age. Though further data are needed to confirm the results, the
study suggests that daughters of women who were given DES may need to be diligent about
receiving regular breast cancer screenings.
Diethylstilbestrol (DES) is a synthetic estrogen that was commonly used to prevent
miscarriages in the 1950s and 1960s. However, subsequent research found that DES was
associated with a significantly increased risk of a certain type of vaginal/cervical
cancer in the daughters of women who were given the drug. Though no definitive studies
have appeared, some researchers believe in utero DES exposure (i.e., exposure to DES while
in the womb) also increases the risk of breast cancer.
To determine whether exposure to DES in the womb increases the risk of breast cancer
later in life, Julie R. Palmer of the Slone Epidemiology Unit at Boston University School
of Medicine and colleagues studied 4,821 women who had been exposed to DES and compared
them to 2,095 unexposed women. The women were followed for an average of 19 years. The
rates of breast cancer among the exposed women’s daughters were then compared with
cases of daughters of non-exposed women.
While pre-natal DES exposure was not associated with a higher risk of breast cancer in
women under 40 years of age, women over 40 who were exposed to DES in the womb were 2.5
times more likely to develop the disease. Thus, while the results are not statistically
significant, the researchers said that an overall 40% increased risk of breast cancer from
DES exposure warrants further investigation.
Approximately 4 million American women were prescribed DES between 1940 and 1971.
According to the DES Cancer Network, as many as 10 million Americans, one in 20, has been
exposed to DES. DES is associated with a rare form of cancer, clear cell adenocarcinoma of
the vagina and cervix. Mothers who were given DES may have a slightly higher risk of
breast cancer compared to non-exposed women.
No special screening guidelines have been recommended for DES-exposed women. The
following guidelines are suggested by several cancer organizations, including the U.S.
National Cancer Institute:
- Women between 20 and 39 years of age should practice monthly breast
self-exams and receive regular clinical breast
exams, performed by a healthcare professional.
- Women between 40 and 49 years of age should practice monthly breast self-exams, receive
yearly clinical breast exams, and receive mammograms every
one to two years.
- Women 50 years of age and older should adhere to the same guidelines as women between 40
and 49, though women should receive yearly mammograms beginning at age 50.
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