Abstract P3-01-01: Insulin, Insulin-like Growth Factor-1 and cycling estrogen predict premenopausal mammographic density.

Background: Mammographic density, a strong biomarker for breast cancer risk, represents epithelial and stromal proliferation. Insulin and insulin-like growth factor (IGF)-1 are suggested to influence cellular proliferation, while estrogen is a key factor in breast cancer development. However, whether the effects of these hormones among premenopausal women are mediated through mammographic density is less known. Material and Methods: Fasting serum insulin, IGF-1, and IGF binding protein (IGFBP)-3 were assessed among 202 healthy premenopausal women (Norwegian Energy Balance and Breast cancer Aspects study-I (EBBA-I). Daily salivary levels of 17β-estradiol throughout an entire menstrual cycle were measured at the reproductive Ecology Laboratory, Harvard University, USA. Computer-assisted mammographic density (Madena) was obtained from digitized mammograms taken at day 7–12 of the menstrual cycle. Uni- and multivariable regression models were used to study the associations between hormones and premenopausal percent mammographic density. Results: Among women with a mean age of 30,7 years, a mean premenopausal percent mammographic density of 29.8 % was observed. Throughout the menstrual cycle when comparing women with a high percent mammographic density (≥28.5%) to women with a low percent mammographic density ( Conclusion: Our study supports that insulin, IGF-1 and IGFBP-3 independently, and in combination with cycling estrogen, predicts premenopausal mammographic density. These hormones may be important biomarkers in breast cancer control and clinical practice. Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P3-01-01.