Vitamin D and Physical Activity on Bone Health

Inclusion Criteria:

• Must be female and have a primary diagnosis of Stage I, II, or III hormone-receptor positive breast cancer.
• Women must be postmenopausal at time of enrollment.
• Must provide informed consent.
• Must be willing to discontinue use of calcium and/or vitamin D supplements.
• Participants must have an ionized serum calcium level within normal limits (1.19-1.29mmol/L) and a total corrected serum calcium of < 10.6 mg/dl.
• Must have a functional capacity rating of ≤ 2 on the Eastern Cooperative Oncology Group (ECOG) performance status when assessed at baseline.132
• Must have the approval of their treating physician (or physician's nurse practitioner or physician's assistant) to participate in sub-maximal physiological fitness testing and a low to moderate home-based walking and progressive resistance exercise program and to receive the 24-week supplementation of vitamin D.
• Must be less than five years from the diagnosis of breast cancer and must be within 6 months of starting treatment with aromatase inhibitors (AI) in accordance with ASCO guidelines.

Exclusion Criteria:

• Subjects with life-threatening conditions that would preclude them from breast cancer treatment including chronic cardiac failure, which is unstable despite medication use, uncontrolled hypertension, uncontrolled diabetes mellitus, or unstable coronary artery disease.
• Patients who had a myocardial infarction within the past year.
• Patients with severe metabolic disorders, which includes phenylketonuria (PKU), homocystinuria, and Fabry's disease, that would preclude them from taking calcitriol.
• Patients with impaired renal function (CRCL < 60 mL/min) or who had kidney stones (calcium salt) within the past 5 years.
• Patients with hypercalcemia (corrected serum Ca ≥ 10.6 mg/dl) or a history of hypercalcemia or vitamin D toxicity.
• Patients currently taking calcium supplements or aluminum-based antacids must be willing to discontinue their use if they are to enroll in the study.
• Patients currently taking vitamin D supplements must immediately discontinue their use if they are to enroll in the study.
• Patients with a known sensitivity to vitamin D.
• Patients who are severely vitamin D deficient (<10 ng/ml).
• Previously verified diagnosed of osteoporosis or severe osteopenia (any t-score ≤ -2.0).
• Women on antiresorptive drugs (e.g. bisphosphonates) within the past year.
• Patients not capable of participating in an exercise intervention due to severe knee arthrosis or ligament/cartilage injuries of the lower extremities.
• Women with malabsorptive syndromes (i.e. cystic fibrosis, chronic pancreatitis) or taking medications that decrease the absorption of fat soluble vitamins (i.e. Orlistat, Questran).