Vitamin D Deficiency, Muscle Pain, Joint Pain, and Joint Stiffness in Postmenopausal Women Receiving Letrozole For Stage I-III Breast Cancer

PRIMARY OBJECTIVES: I. To assess the rate of vitamin D deficiency in breast cancer patients who experience myalgias, arthralgias and/or joint stiffness following initiation of adjuvant letrozole treatment. SECONDARY OBJECTIVES: I. To determine if there is a correlation between letrozole serum levels and the development of myalgias, arthralgias and/or joint stiffness. II. To assess if vitamin D supplementation may alleviate myalgias, arthralgias and/or joint stiffness associated with letrozole in those subjects with vitamin D deficiency. OUTLINE: Patients receive letrozole orally (PO) once daily (QD). Patients, who experience muscle pain, joint pain, or joint stiffness that requires an intervention and who are found to be vitamin D deficient, also receive calcium PO and vitamin D3 PO. Treatment continues for up to 28 weeks in the absence of disease progression or unacceptable toxicity.