Influence of vitamin D (Vit D) on mammographic density (MD) and insulin like growth factor 1 (IGF1): Results of CALGB (Alliance) 70806.

1549 Background: Vitamin D is safe and has breast cancer prevention properties. CALGB 70806 was a randomized phase II trial evaluating the effect of vit D on several breast cancer biomarkers (including MD and serum IGF1). Methods: Premenopausal women were assigned to receive either 2000IU of Vit D or placebo for 12 months, stratified by baseline (BL) vit D level (sufficient vs insufficient). Eligible women were premenopausal, age < 55, with at...