How body mass index affects breast cancer risk in postmenopausal women with and without cardiovascular disease

New research reveals that excess weight is linked to an especially high risk of developing breast cancer in postmenopausal women with cardiovascular disease. The findings are published in Cancer.

Although higher body mass index (BMI) is a known risk factor for breast cancer in postmenopausal women, it’s unclear whether this risk differs among women with and without cardiovascular disease or type 2 diabetes. To investigate, a team led by Heinz Freisling, Ph.D., of the International Agency for Research on Cancer (the specialized cancer agency of the World Health Organization) analyzed data from the European Prospective Investigation into Cancer and Nutrition (EPIC) and UK Biobank on 168,547 postmenopausal women who did not have type 2 diabetes or cardiovascular disease when they agreed to participate.

After a median follow-up of 10.7 years in EPIC and 10.9 years in the UK Biobank, 6,793 postmenopausal women developed breast cancer. In a pooled analysis of both studies, each 5 kg/m² increase in BMI was associated with a 31% higher risk of breast cancer in women who developed cardiovascular disease during follow-up and a 13% higher risk in women without cardiovascular disease. The development of type 2 diabetes did not seem to affect breast cancer risk: Women with or without type 2 diabetes had a similarly elevated breast cancer risk related to higher BMI.

The combination of overweight (BMI ≥ 25 kg/m²) and cardiovascular disease was estimated to lead to 153 more cases of breast cancer per 100,000 people per year than expected.

“The findings of this study could be used to inform risk-stratified breast cancer screening programs,” said Dr. Freisling. “This study should also inspire future research to include women with a history of cardiovascular diseases in weight-loss trials for breast cancer prevention.”