City of Hope Researcher Presents New Data Linking Weight Loss in Postmenopausal Women to Reduced Breast Cancer Risk at 2017 San Antonio Breast Cancer Symposium

December 8, 2017
Study reveals that even losing a modest amount of weight can have a significant reduction in breast cancer risk
DUARTE, Calif. — Research on the link between weight and breast cancer risk in postmenopausal women will be presented by a City of Hope researcher at the 2017 San Antonio Breast Cancer Symposium, held Dec. 5-9. The abstract is titled, “Weight change in postmenopausal women and breast cancer risk in the women’s health initiative observational study,” and was presented at a symposium news conference today.
According to the Centers for Disease Control and Prevention, more than 65 percent of women in the United States are overweight or obese, putting them at higher risk for serious conditions including diabetes, heart disease and some types of cancer.   Since obesity rates are on the rise and breast cancer is among the leading causes of death in American women, researchers evaluated whether losing weight actually lowers a woman’s risk of breast cancer. The study was led by Rowan Chlebowski, M.D., Ph.D., research professor in the Department of Medical Oncology & Therapeutics Research at City of Hope, a world-renowned independent research and treatment center for cancer and diabetes.
Earlier studies have shown that obesity is associated with a higher risk of breast cancer, but were not able to show the benefits of weight loss. This prospective study evaluated the weight and height of postmenopausal women between the ages of 50 and 79 over a three-year period, as well as long-term follow-up. For enrollment, Chlebowski and colleagues analyzed data from the Women’s Health Initiative Observational Study, which tracks the health of postmenopausal women. Participants who had a normal mammogram, no prior breast cancer and were not underweight (body mass index ≥ 18.5) were eligible for enrollment in the study. Findings were based on data from nearly 61,335 women.
According to a press release from the San Antonio Breast Cancer Symposium, modest weight loss (≥ 5 percent) was associated with a 12 percent reduction in breast cancer risk following a multivariable analysis, moderate weight loss (≥ 15 percent) was associated with a 37 percent reduction in breast cancer risk, and only 5 percent of patients developed invasive breast cancer during an average of 11.4 years of follow-up. Although weight gain (≥ 5 percent) was not associated with increased overall breast cancer risk, it was associated with a 50 percent increased risk of triple-negative breast cancer.
“Until now, research has not convincingly demonstrated the impact of weight loss on cancer risk,” said Chlebowski. “Our data find that even modest weight loss is associated with lower cancer risk, which may help increase public awareness of the link between breast cancer and weight after menopause.”
About City of Hope
City of Hope is an independent research and treatment center for cancer, diabetes and other life-threatening diseases. Designated as one of only 49 comprehensive cancer centers, the highest recognition bestowed by the National Cancer Institute, City of Hope is also a founding member of the National Comprehensive Cancer Network, with research and treatment protocols that advance care throughout the world. City of Hope is located in Duarte, California, just northeast of Los Angeles, with community clinics throughout Southern California. It is ranked as one of "America's Best Hospitals" in cancer by U.S. News & World Report. Founded in 1913, City of Hope is a pioneer in the fields of bone marrow transplantation, diabetes and numerous breakthrough cancer drugs based on technology developed at the institution.
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National Institutes of Health (NIH): The National Institute of Diabetes and Digestive and Kidney Diseases Health Information Center. Overweight & Obesity Statistics. August 2017. Accessed December 5, 2017 at:
Centers for Disease Control and Prevention. Overweight and Obesity. Accessed July 25, 2017 at: