Fasting Insulin and Outcome in Early-Stage Breast Cancer: Results of a Prospective Cohort Study

PURPOSE: Insulin, a member of a family of growth factors that includes insulin-like growth factor (IGF)-I and IGF-II, exerts mitogenic effects on normal and malignant breast epithelial cells, acting via insulin and IGF-I receptors. Because of this and because of its recognized association with obesity, an adverse prognostic factor in breast cancer, we examined the prognostic associations of insulin in early-stage breast cancer. PATIENTS AND METHODS: A cohort of 512 women without known diabetes, who had early-stage (T1 to T3, N0 to N1, and M0) breast cancer, was assembled and observed prospectively. Information on traditional prognostic factors and body size was collected, and fasting blood was obtained.…