Insulin-like growth factor-I in relation to premenopausal ductal carcinoma in situ of the breast.

We evaluated the association of plasma insulin-like growth factor-I (IGF-I) and IGF binding protein-3 (IGFBP-3) with risk of breast cancer in a study of 94 cases of premenopausal ductal carcinoma in situ and 76 controls. Compared with women in the lowest tertile of IGF-I, women in the upper two tertiles of IGF-I had an elevated risk for ductal carcinoma in situ. Conversely, compared with women in the lowest tertile of IGFBP-3, women in the upper two tertiles of IGFBP-3 had a decreased risk for ductal carcinoma in situ. After grouping women on the basis of both IGF-I and IGFBP-3, women in the highest two tertiles of IGF-I and the lowest tertile of IGFBP-3 were at notably higher risk than women in the lowest tertile of IGF-I and the highest two tertiles of IGFBP-3 (odds ratio = 3.7; 95% confidence interval = 1.1-12.2). We conclude that the combination of high IGF-I and low IGFBP-3 may increase the risk of premenopausal ductal carcinoma in situ.