The Purpose of this study is to determine whether vitamin D3 supplements will decrease the muscle and bone pain that are reported by women who take Aromatase Inhibitors.

This project will determine the efficacy of vitamin D3 supplements for reducing side effects of treatment with aromatase inhibitors in women with a history of breast cancer that have no evidence of current disease. The aromatase inhibitors (AI) have become a critical component of adjuvant therapy for this population, but they cause bone pain, joint pain, joint stiffness, and muscle weakness in approximately 40% of patients. These symptoms, referred to as aromatase inhibitor-associated musculoskeletal symptoms (AIMSS), decrease quality of life and medication adherence. Identifying effective ways to decrease these symptoms may allow for longer and more adherent medication use and thus may improve disease-free survival. We hypothesize that vitamin D3 may decrease symptoms associated with the use of aromatase inhibitors.

Inclusion Criteria:

• Age ≥ 18 years
• Women with a history of stage I-IIIa invasive breast cancer
• History of hormone-receptor positive cancer (either ER + or PR + or both)
• Are prescribed and are taking anastrozole, letrozole or exemestane for at least one month and have at least 7 months of AI treatment remaining
• Are experiencing AIMSS

Exclusion Criteria:

• Unable to read or understand English
• History of psychiatric disability affecting informed consent or compliance with drug intake
• Malabsorption syndrome or inability to take oral medication
• Has less than 7 months of AI therapy remaining

Adverse events were collected with regard to the organ system