Only AI-treatment was associated with relatively stable IGF-I levels and others have reported no statistically changes in either IGF-I concentrations or the IGF-I/IGFBP-3 molar ratio over the first 6 months (30), although on small study of two groups of 15 patients with advanced breast cancer who received either 0.5 or 2.5 mg letrozole reported a short-term increase in IGF-I but not IGFBP-3 levels during the first 3 months of treatment that was independent of dose (31). Here, IGF1 is linked to breast cancer.