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

Inclusion Criteria:

Patients must have a histologically confirmed diagnosis of Stage I, II or III breast carcinoma
Patients must be prescribed letrozole for adjuvant breast cancer treatment
Prior adjuvant tamoxifen is permitted
Patients must be postmenopausal; for study purposes, postmenopausal is defined as: a prior documented bilateral oophorectomy, or a history of at least 12 months without spontaneous menstrual bleeding, or have a persistently postmenopausal estradiol in the past 6 months without menses, and clinically in menopause at the judgment of the treating physician, or age 60 or older with a prior hysterectomy without oophorectomy, or age less than 60 with a prior hysterectomy without oophorectomy (or in whom the status of the ovaries is unknown), with a documented FSH level demonstrating confirmatory elevation in the postmenopausal range for the lab

Exclusion Criteria:

Diagnosis of Stage IV breast carcinoma
Pre-existing myalgias, arthralgias and/or joint stiffness >= Grade 1, as defined using CTEP CTC identified during baseline physical exam
Inability to understand or cooperate with study procedures
Receipt of investigational drug within 30 days before study entry
Lack of physical integrity of the upper gastrointestinal tract or malabsorption syndrome
Unwillingness to give informed consent
Unwillingness to participate or inability to comply with the protocol for the duration of the study
Patients with serum calcium >= 14 mg/dL
Patients with renal dysfunction defined as glomerular filtration rate <10ml/min calculated using Cockroft-Gault equation