This is a pilot, double-blind, randomized, placebo-controlled study with the following aims:
* To compare the effects of high dose vitamin D versus standard dose vitamin D on musculoskeletal pain in breast cancer patients receiving anastrozole when vitamin D levels are in the insufficient but not deficient range (10 to 29 ng/ml).
* To evaluate the prevalence of vitamin D insufficiency/deficiency in post-menopausal women with a history of breast cancer who are treated with anastrozole and have musculoskeletal symptoms versus those who are asymptomatic.
* To establish correlations between levels of vitamin D, the levels of PTH, the degree of bone loss and the severity of musculoskeletal symptoms.
* To evaluate the effect of standard dose versus high dose Vitamin D replacement on bone density in post-menopausal women with a history of breast cancer who are treated with anastrozole and have musculoskeletal symptoms.
