There have been few studies of the effect of serum insulin levels on the invasive phenotype in breast cancer, or metastatic behavior and prognosis, although two studies by Goodwin and her colleagues did find that elevated plasma insulin concentrations in both non-diabetic premenopausal and postmenopausal breast cancer patients were associated with an increased risk of recurrence at distant sites and a poor prognosis [65,66]. Here, INS is linked to breast cancer.