A Study of High-Dose Vit D Versus Standard of Care Vit D Supplementation

This is a randomized, open-label study designed to evaluate the effect of high dose vitamin D versus standard of care vitamin D supplementation on bone health and arthralgias. The randomization will be stratified by hormone receptor status (positive versus negative). The primary objective is to compare the effect of high dose vitamin D to the current standard vitamin D treatment administration algorithm on bone health, as measured by percent change from baseline in bone mineral density (g/cm2), in young women with non-metastatic breast cancer who receive systemic therapy.