Study of Vitamin D for Premenopausal Women at High Risk for Breast Cancer

This proposal is for a pilot study of 20 premenopausal women at high risk for breast cancer development who will receive high dose vitamin D3, cholecalciferol 20,000 IU (2 capsules) weekly, or 30,000 IU (3 capsules) weekly, for 1 year. The primary objective of this study is to determine the feasibility of a 1-year intervention of vitamin D in this study population. Secondary objectives include evaluating the biologic effects of vitamin D supplementation on blood based and image-based biomarkers.

Vitamin D has diverse biological effects relevant to carcinogenesis, including known cross-talk between the vitamin D receptor (VDR) and insulin-like growth factor (IGF) signaling pathways. Based upon observational data, women with serum 25(OH) D levels greater than 40-50 ng/ml had a 50% lower risk of breast cancer compared to women with vitamin D deficiency. Vitamin D is a fat-soluble vitamin which is produced in the body and may come from food sources. Epidemiologic studies suggest that vitamin D may influence breast cancer development, which has resulted in increased interest in the use of vitamin D for the treatment and prevention of breast cancer. Numerous experimental studies have shown that vitamin D compounds have anti-carcinogenic properties against breast cancer. Given the epidemiologic data and the extensive preclinical evidence of the anti-tumor effects of vitamin D, it is therefore reasonable to test the biological effects of high-dose vitamin D in early phase clinical trials. The investigators hypothesize that vitamin D3, cholecalciferol, will modulate biomarkers of breast cancer risk. The relationship between vitamin D status and mammographic density (MD), a strong predictor of breast cancer risk, remains unclear \[8\]. MD refers to the relative proportions of radiolucent fat and radiodense epithelial and stromal tissue and may serve as a useful intermediate biomarker for breast cancer risk assessment in investigations of potential chemopreventive agents. Cross-sectional studies evaluating the association between vitamin D intake and MD observed an inverse association among premenopausal women, particularly with high serum IGF-1 and low serum IGF binding protein-3 (IGFBP-3). However, there is limited data on the biologic effects of vitamin D supplementation for breast cancer prevention in human intervention trials.