Metabolic syndrome linked to breast cancer

New research suggests that a set of risk factors for heart disease and type 2 diabetes, known as the metabolic syndrome, could be related to the risk of breast cancer in post-menopausal women.

People with the syndrome have excess fat around their middle, high levels of glucose in their blood, resistance to the blood-glucose-lowering hormone insulin, high cholesterol, and high blood pressure, Dr. Geoffrey C. Kabat of the Albert Einstein College of Medicine in Bronx, New York and his colleagues note in their report.

While researchers have looked at separate components of the syndrome and breast cancer risk, Kabat and his team add, results of these studies have been "inconclusive," and no one has investigated the syndrome as a whole in relation to risk of breast cancer.

They looked at a subset of 4,396 women participating in a large study of postmenopausal women's health called the Women's Health Initiative.

Women who had metabolic syndrome at the study's outset were at no greater risk of developing breast cancer during follow-up, which averaged about 8 years.

But individual components of the syndrome - especially high blood glucose, high levels of triglycerides, and high diastolic blood pressure - were linked to increased risk when the researchers looked at these variables 1 year before the breast cancer diagnosis.

"If this is confirmed by further studies, this would suggest that impaired glucose tolerance and insulin resistance play a role in breast cancer," Kabat told Reuters Health via email. The conventional wisdom, he added, has been that obesity boosts breast cancer risk by increasing estrogen levels. "Because insulin and insulin-like growth factors stimulate growth in breast cancer cells, we need to better understand the interplay of insulin, estrogen, and components of the metabolic syndrome in influencing breast cancer risk," the researcher said.

"Breast cancer is a complex disease, and it is important to try to understand the mechanisms by which excess body weight and lack of physical activity influence the risk of this disease," he added.

While it's too soon to make public health recommendations based on these preliminary findings, Kabat said, the results do suggest that current advice to maintain a healthy weight and exercise could be helpful in terms of breast cancer risk.

SOURCE: Cancer Epidemiology, Biomarkers and Prevention, July 2009.