Abstract
Obesity contributes to an estimated forty-percent, or 630,000 cases, of malignant neoplasms diagnosed in the United States[1] and higher body mass index (BMI) has been associated with at least seventeen types of solid tumors, including 9% of all breast cancer cases. In this review, we discuss the impact of obesity and consequences of obesity, including the metabolic syndrome and type 2 diabetes mellitus, on breast cancer risk and recurrence. Recent work has identified multiple molecular mechanisms that may underlie the association between obesity and breast cancer. In particular, insulin resistance, increased inflammatory cytokines, leptin signaling, and adipokine signaling have been shown to affect breast cancer risk and outcomes. While obesity is associated with higher breast cancer incidences and worse breast cancer outcomes, several risk reduction methods have been shown to attenuate these risks. Both metformin and statins have been shown to improve disease free survival and overall survival compared to non-users. Metformin also has been associated with lower risk of breast cancer incidence. Furthermore, increased physical activity and weight loss have been shown to decrease risk of breast cancer, especially in post-menopausal women. These studies have emphasized the potential impact that lifestyle changes can have on breast cancer risk and outcomes, and demonstrate the need for randomized control trials to evaluate the roles of metformin and statins for the treatment and chemoprevention of breast cancer.