SABCS 2017: Postmenopausal Women Who Lose Weight May Have Reduced Breast Cancer Risk

Key Points

  • Of the 61,335 patients enrolled in the study, 3,061 developed invasive breast cancer during an average of 11.4 years of follow-up.
  • Compared with women with stable weight, those who lost weight (≥ 5% weight change) were 12% less likely to develop breast cancer following multivariable analysis.
  • Weight loss of ≥ 15% was associated with a 37% reduction in breast cancer risk.   
  • Although weight gain (≥ 5% weight change) was not associated with an increased overall breast cancer risk, it was associated with more than a 50% increased risk of triple-negative breast cancer.

Postmenopausal women who lose weight may have a significantly reduced chance of developing breast cancer, according to data presented by Chlebowski et al at the 2017 San Antonio Breast Cancer Symposium (Abstract GS5-07).

“Breast cancer is among the leading types of cancer and causes of death in American women,” said Rowan Chlebowski, MD, PhD, Research Professor in the Department of Medical Oncology and Therapeutics Research at City of Hope in Duarte, California. “Obesity rates have been increasing in the United States. We wanted to determine if there was a link between obesity and breast cancer risk.”

Several studies have associated high body mass index (BMI) with increased breast cancer risk, noted Dr. Chlebowski. Although this risk factor is largely preventable, it is estimated that more than 65% of American women are overweight or obese. 

“We wanted to determine if weight loss was associated with lower breast cancer incidence, as studies have not been able to consistently show that losing weight reduces the risk of breast cancer,” said Dr. Chlebowski. Past studies have been limited to analyses with self-reported measurements, whereas the prospective study conducted by Dr. Chlebowski and colleagues utilizes a short-term, 3-year period of measured body weight and height followed by a long period of follow-up. 

Study Details

Dr. Chlebowski and colleagues analyzed data from the Women’s Health Initiative Observational Study. This program tracks the health of postmenopausal women between the ages of 50 and 79 years. Participants who had a normal mammogram, no prior breast cancer, and were not underweight (BMI ≥ 18.5 kg/m2) were eligible for enrollment in the study. Measurements for height and weight were obtained upon enrollment, and measurements were reassessed 3 years following. 

At baseline, 41% of women were of normal weight, 34% were overweight, and 25% were obese. 

Of the 61,335 patients enrolled in the study, 3,061 developed invasive breast cancer during an average of 11.4 years of follow-up. Compared with women with stable weight, those who lost weight (≥ 5% weight change) were 12% less likely to develop breast cancer following a multivariable analysis. Weight loss of ≥ 15% was associated with a 37% reduction in breast cancer risk.   

“In the 3-year window of the study, relatively modest weight loss was associated with significant lowering of breast cancer incidence,” said Dr. Chlebowski. “From this study, we have evidence that a weight loss strategy can be effective in lowering breast cancer risk in postmenopausal women.”

Although weight gain (≥ 5% weight change) was not associated with an increased overall breast cancer risk, it was associated with more than a 50% increased risk of triple-negative breast cancer.

Disclosure: The study was supported by the National Institutes of Health. Dr. Chlebowski is a consultant for Novartis, AstraZeneca, Genentech, and Amgen.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.


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