Higher
Breast Cancer Risk Found for DES Daughters
Women whose mothers took DES, a synthetic estrogen,
while pregnant have nearly double the risk of breast cancer, according
to a report in the journal Cancer Epidemiology,
Biomarkers and Prevention.
Called DES, diethylstilbestrol was prescribed from
1938 through 1971 to prevent miscarriage and other pregnancy complications.
During that time, as many as 10 million American
women took DES during pregnancy, the Centers
for Disease Control and Prevention (CDC) estimates.
The study compared women exposed to DES in utero
(in the uterus) to a group of comparably aged women who were not exposed
to the excess hormone levels.
"Women who were exposed to DES have been wondering
about this for a long time," says the study's lead author, Julie Palmer,
Sc.D., a professor of epidemiology at Boston University's School of
Public Health.
"We found the risk of breast cancer was about two
times as high in the exposed women compared to unexposed women among
those 40 years and older," notes Dr. Palmer.
Although research published in 1953 refuted the
notion that DES could prevent the loss of pregnancy or pregnancy difficulties,
physicians still continued to prescribe the medication.
In 1971, the US Food and
Drug Administration (FDA) advised physicians to stop prescribing
DES because it was linked to a rare form of vaginal and cervical
cancer - clear cell adenocarcinoma - in daughters of women who took
DES while pregnant.
These women eventually came to be known collectively
as "DES daughters," according to the CDC.
Besides the increased risk of clear cell adenocarcinoma,
being a "DES daughter" also increases the risk of reproductive
tract defects, such as a T-shaped uterus, infertility, and pregnancy
complications, such as ectopic pregnancy or pre-term birth, according
to the CDC.
Boys born to mothers who took DES may experience
abnormal, though non-cancerous, growths on their testicles.
Previous research had suggested that prenatal hormone
levels of DES may affect the risk of breast cancer later in life. And
women who took DES have higher rates of breast cancer.
So, the researchers behind the new study wanted
to assess what the actual risk of breast cancer was for women exposed
to DES in utero.
The scientists recruited 4,817 women who had been
exposed to DES in utero and 2,073 women born in the same time period,
but who had not been exposed to the medication.
Most of the women in both groups were born in the
1950s, and nearly all were Caucasian.
During 2001 to 2003, the women were sent questionnaires,
and 102 women - 76 in the DES-exposed group and 26 in the control group
- reported a diagnosis of breast cancer.
After compensating for other breast-cancer risk
factors, the researchers found that women who were exposed to DES in
utero had a 91 percent higher risk of breast cancer after age 40, and
a three-fold increased risk of breast cancer after age 50, when compared
to women not exposed to the medication.
"These women received a much higher exposure to
synthetic estrogen than would normally be there during a regular pregnancy," explains
Dr. Palmer.
She theorizes that the extra estrogen spurs the
development of additional breast stem cells, and because there are
a greater number of breast stem cells, there is an increased risk of
cancer.
Dr. Jay Brooks, chairman of hematology and oncology
at the Ochsner Health System in Baton Rouge, La., says, "This is an
interesting study that shows we still don't know all of the long-term
effects on women who took DES and their female offspring.
"This is important, but should be kept in perspective," he
adds. "While it is an increased risk, it's along the same order of
escalation of risk as having a family history of breast cancer or of
not having a child by the age of 30."
Dr. Brooks says if women - all women, whether exposed
to DES or not - wanted to decrease their risk of breast cancer, they
should maintain a normal weight, or lose excess weight.
Dr. Palmer adds that some research has shown that
regular physical activity may be helpful in reducing your risk of breast
cancer.
Women who know they were exposed to DES in utero
should carefully discuss the use of post-menopausal hormones with their
physician, she suggests.
Dr. Palmer also notes that all women should have
regular mammogram screenings to detect breast cancer in its earliest
stages.
Depending on what additional risk factors women
exposed to DES may have, Dr. Brooks says women might want to discuss
the potential risks and benefits of using the medications tamoxifen
or raloxifene, because these medications block the action of estrogen,
which can fuel some breast tumors.
Always consult your physician for more information.
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