High insulin levels in newly diagnosed breast cancer patients reflect underlying insulin resistance and are associated with components of the insulin resistance syndrome.

BACKGROUND: High insulin levels have been associated with poor outcomes in breast cancer. Our goal was to investigate whether hyperinsulinemia was associated with insulin resistance in a cohort of newly diagnosed locoregional breast cancer patients and to examine associations of hyperinsulinemia with the broader insulin resistance syndrome (IRS). METHODS: Five hundred and four women with T1-3, N0-1, M0 breast cancer provided fasting blood that was analyzed for glucose, insulin and lipids. They underwent anthropomorphic measurements and provided information on diet, exercise and sleep. Relationships of insulin with three validated indices of insulin resistance and with attributes of the IRS were examined. RESULTS: High insulin levels were strongly correlated with insulin resistance calculated using the three indices of insulin resistance/sensitivity (Spearman r=0.83-0.98). Hyperinsulinemia was also associated with other components of the IRS (obesity, high waist-hip ratio, lipid profile). CONCLUSIONS: High insulin levels in women with locoregional breast cancer reflect the presence of insulin resistance and are associated with other components of the IRS. These observations have implications for the development of therapies that target hyperinsulinemia in early stage breast cancer and for the long-term management of breast cancer survivors.