Obesity and breast cancer: risk, outcomes, and future considerations.

The proportion of adults who are obese has increased dramatically in the United States over the last 30 years. Obesity has been linked to an increased risk of developing a number of malignancies, including postmenopausal breast cancer. Evidence also suggests that obesity at the time of breast cancer diagnosis is linked to an increased risk of breast cancer-specific and overall mortality in both premenopausal and postmenopausal women with early-stage breast cancer. Obesity is linked to an increased risk of secondary malignancies in women with early breast cancer, and studies suggest that weight gain after diagnosis increases overall mortality. Despite the data linking obesity to poor outcomes in women with early breast cancer, there are currently no data from randomized trials testing the impact of weight loss on breast cancer outcomes. A number of recent randomized controlled trials have shown that weight loss interventions are feasible in obese survivors of breast cancer, yielding loss of 5% to 6% of body weight, and several ongoing randomized phase 3 clinical trials are evaluating the effect of weight loss interventions on breast cancer outcomes. These studies will help define the role of weight loss in the management of obese women with early breast cancer.