Aromatase Inhibitor-Associated Musculoskeletal Symptoms in Non-Metastatic, Post Menopausal Breast Cancer Patients

Inclusion Criteria: * Women 18 years and older with non-metastatic hormone receptor (ER and/or PR) positive breast cancer who are eligible for and planning on starting treatment with an AI within one month of signing consent. * Postmenopausal, defined as at least one of the following: a) amenorrhea for at least 12 months b) prior bilateral oophorectomy at least 2 years prior to trial registration. Exclusion Criteria: * History of autoimmune connective tissue disease, such as rheumatoid arthritis, lupus, or other autoimmune conditions affecting joints. * Treatment with steroid (for any condition, except for chemotherapy premedication) within 30 days of trial registration. * Prior treatment with an AI (patients previously or currently on tamoxifen are eligible as long as patients are off tamoxifen for 2 weeks prior to baseline blood draw) * Active or ongoing infection * Known metastatic disease * Known history of HIV or hepatitis infections * Ongoing radiation therapy (radiation must have been completed 2 weeks prior to starting treatment with an AI) * Non-invasive (DCIS, LCIS) cancer only (no diagnosis of invasive cancer) * Pregnant or lactating * Unable to speak, read, and write in English