American Association for Cancer Research

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New Approach Evaluates Effect of Physical Activity on Estrogen Metabolism in Postmenopausal Women


April 9, 2013

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  • Study used direct measures of physical activity and comprehensive analysis of urinary estrogen levels.
  • Increased physical activity was related to lower urinary levels of estrogens and four estrogen metabolites.
  • These data have implications for understanding the link between physical activity and breast cancer risk.
WASHINGTON, D.C. — Researchers have generated new insights into the ways in which physical activity affects how much estrogen is broken down and secreted in the urine of postmenopausal women. These findings enhance understanding of the potential biological mechanisms linking increased physical activity and decreased risk for breast cancer in postmenopausal women, according to the scientist who presented the data at the AACR Annual Meeting 2013, held in Washington, D.C., April 6-10.

Previous studies have suggested that increased physical activity may reduce the risk for breast cancer among postmenopausal women, and that this might be a result of physical activity lowering endogenous estrogen levels, according to Cher Dallal, Ph.D., a National Cancer Institute (NCI) cancer prevention fellow. However, few studies have evaluated the influence of physical activity on the breakdown of estrogens in postmenopausal women. This breakdown process, called estrogen metabolism, results in a variety of molecules known as metabolites.

“This is the first study to consider the relationship between accelerometer-measured activity and a panel of estrogen metabolites measured in urine,” said Dallal. “We hoped by using direct measures to examine this relationship that we could improve our knowledge of how these factors may influence cancer risk among postmenopausal women.”  

Dallal and colleagues studied 540 healthy, postmenopausal women who were enrolled in the NCI Polish Breast Cancer Study, conducted from 2000 to 2003. None of the women were taking menopausal hormone therapy. The investigators measured physical activity by accelerometer, which is a small device that women wore on their waists during waking hours for seven days. According to Dallal, accelerometers provide objective readings of physical activity compared with participants’ self-reports, which have been the predominant measure in previous studies.

Women also provided a 12-hour urine sample. The researchers tested the samples for estradiol and estrone, two “parent” estrogens, plus 13 different estrogen metabolites using a new assay developed by the NCI. According to Dallal, this novel assay can detect multiple urinary estrogens, compared with those used in previous studies that only measured one or two metabolites individually.

The researchers found that increased physical activity was associated with lower levels of parent estrogens. In addition, higher levels of physical activity were associated with lower levels of four specific estrogen metabolites. Dallal cautions, however, that further research on estrogen metabolism will be needed to understand how these metabolites play a role in mediating breast cancer risk.

“By using these new tools to study the relationship between activity and estrogen metabolism, we hope to get closer to uncovering the combination of parent estrogens, metabolites and metabolism pathways that are related to a lower-risk profile of breast cancer,” said Dallal.

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About the American Association for Cancer Research
Founded in 1907, the American Association for Cancer Research (AACR) is the world’s first and largest professional organization dedicated to advancing cancer research and its mission to prevent and cure cancer. AACR membership includes more than 34,000 laboratory, translational and clinical researchers; population scientists; other health care professionals; and cancer advocates residing in more than 90 countries. The AACR marshals the full spectrum of expertise of the cancer community to accelerate progress in the prevention, biology, diagnosis and treatment of cancer by annually convening more than 20 conferences and educational workshops, the largest of which is the AACR Annual Meeting with more than 17,000 attendees. In addition, the AACR publishes eight peer-reviewed scientific journals and a magazine for cancer survivors, patients and their caregivers. The AACR funds meritorious research directly as well as in cooperation with numerous cancer organizations. As the scientific partner of Stand Up To Cancer, the AACR provides expert peer review, grants administration and scientific oversight of team science and individual grants in cancer research that have the potential for near-term patient benefit. The AACR actively communicates with legislators and policymakers about the value of cancer research and related biomedical science in saving lives from cancer. For more information about the AACR, visit www.AACR.org.

Media Contact:
Jeremy Moore
(215) 446-7109
Jeremy.Moore@aacr.org
In Washington, D.C.,
April 6-10, 2013:

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