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As part of the Women’s Health Initiative, a recent study has reported as association between BMI and breast cancer risk.

A recent study published in the Journal of the American Medical Association has reported on the link between obesity and risk of breast cancer. With previous evidence linking obesity and breast cancer, researchers set out to investigate the associations between being overweight or obese and the risk of postmenopausal breast cancer.

The participants for the study were from the Women’s Health Initiative clinical trial. Over 67 000 women between 50 and 79 years were included in the study. The results revealed that overweight and obese women had an increased risk of developing invasive breast cancer when compared to women who were normal weight. Additionally, this risk increased as BMI increased, demonstrating the greatest risk of breast cancer in women with a BMI of 35.0 or greater, with a reported 58% increased risk of invasive breast

The results also showed that the association between BMI and breast cancer risk was specific according to the subtype of cancer. The sub-types showing an increased risk were estrogen receptor and progesterone receptor positive breast cancers. Further analysis demonstrated that obesity was associated with more advanced breast cancer, which included measures of tumor size and lymph node metastasis.

Overall the results demonstrate and increase in postmenopausal breast cancer risk with increasing BMI. This was particularly found for both estrogen receptor positive and progesterone receptor positive breast cancers. The researchers suggest that due to the fact that these sub-types of breast cancer are hormonally influenced, the increased risk may be derived from the higher levels of hormones produced by adipose tissue in overweight and obese women. Alternately, they suggest that increased levels of leptin present in overweight and obese women, which can also increase estrogen levels, may contribute to the increased risk. The researchers suggest that future study should assess the potential mechanisms that may be involved, in addition to clinical trials assessing obesity prevention and treatment on breast cancer risk.



Neuhouser, ML, Aragaki, AK, Prentice, RL, Manson, JE, Chlebowski, R, Carty, CL, Ochs-Balcom, HM, Thomson, CA, Caan, BJ, Tinker, LF, Peragallo Urrutia, R, Knudtson, J, Anderson, GL. “Overweight, Obesity, and Postmenopausal Invasive Breast Cancer Risk :  A Secondary Analysis of the Women’s Health Initiative Randomized Clinical Trials” JAMA Oncology, Published Online June 11, 2015.

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Written by Deborah Tallarigo, PhD

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