Women with high body fat at increased risk of breast cancer: JAMA

Researchers from Memorial Sloan Kettering Cancer Center have found that in postmenopausal women High body fat levels are associated with increased breast cancer risk. The Secondary Analysis of a Randomized Clinical Trial and Observational Study has been reported in JAMA Oncology.

Obesity is associated with an increased risk of breast cancer, including the estrogen receptor (ER)–positive subtype in postmenopausal women. The recognition of obesity as a risk factor for several cancers is largely based on the use of body mass index BMI but it is a crude measure of body size that does not discriminate between adiposity and muscle.

The researchers conducted this study to evaluate whether increased levels of body fat in women with a normal body mass index were associated with an elevated risk of breast cancer.

They enrolled 3460 postmenopausal women with normal body mass index in the Women’s Health Initiative randomized clinical trial and observational study. Women included in the WHI had normal mammogram findings at baseline or mammogram findings not suggestive of cancer within 2 years before enrollment.

At baseline, self-administered questionnaires were used to collect information on demographic characteristics, menstrual history, reproductive history, exogenous hormone use, family history, medical history, and diet and lifestyle factors, and a fasting blood sample was obtained. The subjects underwent body fat measurement with dual-energy x-ray absorptiometry (DXA) at 3 US designated centres with follow-up.

The researchers found that higher body fat levels measured by dual-energy x-ray absorptiometry were associated with an increased risk of invasive breast cancer at a median follow-up of 16 years.

The conclusion was that Postmenopausal women with higher body fat levels are at elevated risk for breast cancer despite having a normal body mass index.“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,” the study concluded.

This study validates recent evidence that a subset of women with normal BMI and excess body fat may be at increased risk for breast cancer.