Overweight & Obese Postmenopausal Women at Increased Risk of Breast Cancer

Postmenopausal women who are obese or overweight have an increased risk of developing breast cancer, according to a new study.

The findings published in JAMA Oncology suggest that older women who are overweight, obese and are postmenopausal have a higher risk of contracting invasive breast cancer compared to same-aged women who have normal weight.

In addition, obese women are more likely to have large and fast-growing tumors and have the disease spreading into the lymph nodes, according to Medical Daily.

Dr Marial L. Neuhouser, of Seattle's Fred Hutchison Cancer Research Center, and co-authors analyzed the link between being overweight or obese to risk of getting postmenopausal invasive breast cancer.

They analyzed the height, weight and mammograms of 67,142 postmenopausal women according to The Women's Health Initiative (WHI) protocol. They found 3,388 invasive breast cancer cases from these women aged 50 to 79 enrolled from 1993 to 1998, with a median of 13 years follow-up.

The researchers then grouped the women according to their body mass index (BMI). A BMI of less than 25 is normal, BMI between 25 and 30 is overweight and BMI over 30 is obese and 35 or above is considered morbidly obese, according to Reuters.

Approximately 5 percent of women in each BMI group received a breast cancer diagnosis during the study period, but the likeliness increased with weight. Women who were considered morbidly obese (BMI - 35) had a 56 percent increased risk of developing invasive breast cancer compared to women with normal BMI.

They also found that majority of the obese women had an 86 percent chance of developing poorly differentiated tumors that grow at a fast pace.

The findings showed that normal-weight women who gained weight during the study increased their chances of breast cancer by 35 percent. However, obese or overweight women who lost weight did not decrease their breast cancer risk.

"Obesity is known to increase estrogens in the postmenopausal women because estrogen is made by fat tissue," said Neuhouser, as per Science World Report. "Fat tissue also secretes inflammatory factors and is associated with insulin resistance -- all of which may increase breast cancer risk."

The study authors noted that more than two-thirds of women in the U.S. are overweight or obese.

"Overweight and obesity are a growing global challenge and the increased burden of malignant disease, to which it contributes, is another one. Their report helps focus our thinking and motivates us to pursue a deeper understanding of why overweight and obesity are a problem so that we can plan more effective and thoughtful responses," said doctora Clifford Hudies, of New York's Memorial Sloan Kettering Cancer Center, and Andrew Dannenberg of, Weill Cornell Medical College, in a related commentary, Medical Xpress has learned.