Obesity After Menopause Seen to Increase Breast Cancer Risk

American Cancer Society
Tuesday, 18 June 2002

Large American Cancer Society Study Reinforces Evidence of Dangers of Being Overweight

Women who are overweight or obese after menopause have a greater risk of dying from breast cancer than women who maintain a normal weight, according to findings from the American Cancer Society's Cancer Prevention Study II (CPS-II). The findings were published as an article entitled "Body mass index, height and postmenopausal breast cancer mortality in a prospective cohort of United States women" in the May 2002 issue of Cancer Causes & Control, the official journal of the Harvard Center for Cancer in Humans, Cambridge, MA.

Overweight and obesity were measured by body mass index (BMI), a measure of weight that is adjusted for height. Breast cancer mortality rates increased continually and substantially with increasing BMI, and were twice as high in obese women than in lean women. Based on the results of this study, the authors estimated that 30% to 50% of breast cancer deaths among postmenopausal women in the US may be attributed to overweight and obesity.

"Because overweight and obese women are at increased risk of both getting breast cancer and dying from their disease, it is essential that these women have regular mammograms," said Eugenia Calle, PhD, director of analytic epidemiology at the Society and one of the authors of the study.

"The good news", Dr. Calle added, "is that unlike many risk factors for breast cancer, weight is modifiable. If women can avoid weight gain in adulthood and maintain a lean to normal weight throughout life , they will be at lower risk of dying from breast cancer."

Most previous studies of how weight affects a woman's breast cancer risk have been unable to examine risk across a wide range of body mass , and few studies have looked at breast cancer mortality. In addition, most studies have been too small to investigate potential differences between weight and breast cancer mortality in subgroups of women. CPS II included 424,168 postmenopausal women who were cancer-free when they enrolled in the study in 1982. After 14 years of follow-up, 2,852 women had died of breast cancer.

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