The primary hypothesis is that high dose vitamin D3 plus standard dose vitamin D3 prevents the worsening of musculoskeletal symptoms when compared to a standard dose vitamin D3 treatment. This protocol will examine the relationship between vitamin D levels (25-hydroxyvitamin D) and various quality of life measures in women being treated with letrozole as standard care for early stage breast cancer. All subjects received letrozole and a standard dose of vitamin D3 (600 IU daily). Randomization was between high dose vitamin D3 (30,000 IU once per week) vs. a blinded, matched placebo,
The primary purpose is to determine if high dose vitamin D3 reduces the incidence of musculoskeletal symptoms associated with the aromatase inhibitor letrozole in women with early stage breast cancer and low serum vitamin D levels.