Postmenopausal women with higher body fat levels are at elevated risk for breast cancer despite having a normal body mass index., according to a study from the Women’s Health Initiative in JAMA Oncology.
Obesity is associated with an increased risk of breast cancer, including the estrogen receptor (ER)–positive subtype in postmenopausal women. Whether excess adiposity is associated with increased risk in women with a normal body mass index (BMI) is unknown.
This ad hoc secondary analysis of the Women’s Health Initiative (WHI) clinical trial and observational study cohorts was restricted to postmenopausal participants with a BMI ranging from 18.5 to 24.9. Women aged 50 to 79 years were enrolled from October 1, 1993, through December 31, 1998. Nearly 3500 postmenopausal women without a history of breast cancer and a baseline BMI of 18.5 to 24.9 had their fat mass assessed by dual-energy X-ray absorptiometry at baseline and periodically during follow-up. After a median 16-years, 5% were diagnosed with invasive breast cancer. Women in the highest quartile of whole-body fat mass or trunk fat mass at baseline had nearly a 90% increased breast cancer risk, compared with those in the bottom quartiles.
The authors conclude: “In postmenopausal women with normal BMI, relatively high body fat levels were associated with an elevated risk of invasive breast cancer and altered levels of circulating metabolic and inflammatory factors. Normal BMI categorization may be an inadequate proxy for the risk of breast cancer in postmenopausal women.”
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Source: NEJM journal watch & JAMA oncology
