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Estrogen
found as link between obesity and breast cancer in postmenopausal women
Karen
Carter Mallet
Eurekalert,
August 20, 2003
PHILADELPHIA (August 13, 2003) – Researchers have known that obesity is associated with an increased risk of breast cancer in postmenopausal women, but a new study now explains why. According to research published in the August 20, 2003, issue of the Journal of the National Cancer Institute obesity increases the risk of breast cancer in postmenopausal women by increasing the amount of estrogens in the blood. High levels of estrogen definitively have been linked as a causative factor for breast cancer. The finding was
reported by the Endogenous Hormones and Breast Cancer Collaborative Group.
Joanne F. Dorgan, M.P.H, Ph.D., an epidemiologist at Fox Chase Cancer
Center, is the lead investigator of one of eight cohorts included in the
analysis. "We've known
that postmenopausal women who are overweight have an increased risk of
breast cancer, and the risk also is higher in women who have higher levels
of estrogens in their blood," said Dorgan. "Our results suggest
that obesity increases breast cancer risk in postmenopausal women by
increasing serum concentrations of estrogens." For the study,
researchers analyzed the blood donated by women in eight cohorts in the
United States, Europe and Asia. All the women were cancer-free and were
not using hormone replacement therapy when the blood was collected. The
women were followed for two to 12 years and 624 women developed breast
cancer. Hormones in their blood were compared with the hormones from 1,640
cancer-free women who were the same age when blood was donated as the
women who developed breast cancer. Obesity was measured by body mass index
(BMI), a measure of weight that is adjusted for height. Most of the
established risk factors for breast cancer are either fixed (family
history and genotype) or not amenable to modification (age at menarche,
number of and ages at pregnancy, age at menopause). "This is an
example of a risk factor that a woman can control," Dorgan said.
"The effect of obesity on breast cancer risk is important because the
prevalence of obesity is high and increasing." According to Dorgan,
the estimated prevalence of obesity in U.S. women aged 60 to 74 increased
from 29 percent between 1988 and 1994 to 40 percent in 1999-2000. "Obesity is a
risk factor for other diseases such as heart disease and diabetes,"
Dorgan added. "Women need to know that breast cancer has been added
to that ominous list." ### The Endogenous
Hormones and Breast Cancer Collaborative Group is international consortium
that includes epidemiologists from the United States, England, Italy, and
Japan. The group conducts research on the relationship of endogenous
hormones to breast cancer development. For the current analysis,
researchers from eight of the nine cohorts pooled their data so they could
evaluate whether higher serum estrogens in heavier women explains the
relationship of obesity with breast cancer risk in postmenopausal women. The nine cohorts and
the principal investigators who make up the Endogenous Hormones and Breast
Cancer Collaborative Group include the Columbia, Mo., cohort (JF Dorgan);
the Guernsey, UK, cohort (TJ Key); Nurses' Health Study cohort (SE
Hankinson); New York University Women's Health Study cohort (PG Toniolo);
the ORDET, Italy, cohort (F Berrino); the Rancho Bernardo cohort (E
Barrett-Connor); the RERF, Japan, cohort (M Kabuto); the SOF cohort (JA
Cauley); and the Washington County, Md., cohort (KJ Helzlsouer). Fox Chase Cancer
Center, one of the nation's first comprehensive cancer centers designated
by the National Cancer Institute in 1974, conducts basic and clinical
research; programs of prevention, detection and treatment of cancer; and
community outreach. For more information about Fox Chase activities, visit
the Center's web site at http://www.fccc.edu
or call 1-888-FOX CHASE. Copyright
© 2002 Global Action on Aging
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