Modulation of Breast Cancer Risk Biomarkers by High Dose Vitamin D

Protocol Objectives: To determine if high dose vitamin D3 given to premenopausal women who initially have insufficient levels of 25-hydroxy vitamin D (\<30 ng/ml) will raise 25(OH)D levels above the 50 ng/ml level considered to be required for breast health. If so, will certain risk biomarkers for development of breast cancer be reliably and favorably modulated? The primary endpoint will be a decrease in mammographic breast density (percent area considered at increased density). Change in proliferation (a decrease as assessed by Ki-67) will also be examined. Modulate of expression of genes important in breast cancer risk or reflective of vitamin D's mechanism of action will be studied using quantitative real time polymerase chain reaction (qRT-PCR). Study Design: The study is a single-arm open label clinical trial. Women who are high risk for development of breast cancer on the basis of family or personal history will undergo random periareolar fine needle aspiration (RPFNA) to acquire breast cells for assessment of gene expression by qRT-PCR. Women with mammographic density \>10% will be eligible for enrollment. All subjects will receive high dose vitamin D3 (3 capsules of 10,000 IU of vitamin D3 every week for 6-8 months). At that time, a repeat RPFNA and mammogram will be performed. Measurement of serum levels of 25(OH)D will be performed at baseline, 3 months, and 6 months.