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-receptorpositive 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.

• Participants must be slightly vitamin D deficient (serum vitamin D level <32ng/ml)

• Must have a functional capacity rating of ≤ 2 on the Eastern Cooperative OncologyGroup (ECOG) performance status when assessed at baseline.132

• Must have the approval of their treating physician (or physician's nursepractitioner or physician's assistant) to participate in sub-maximal physiologicalfitness testing and a low to moderate home-based walking and progressive resistanceexercise 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 12 months of starting treatment with aromatase inhibitors (AI) in accordance withAmerican Society of Clinical Oncology (ASCO) guidelines.

Exclusion Criteria:

• Subjects with life-threatening conditions that would preclude them from breastcancer treatment including chronic cardiac failure, which is unstable despitemedication use, uncontrolled hypertension, uncontrolled diabetes mellitus, orunstable 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 takingcalcitriol.

• 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 ofhypercalcemia or vitamin D toxicity.

• Patients currently taking calcium supplements or aluminum-based antacids must bewilling to discontinue their use if they are to enroll in the study.

• Patients currently taking vitamin D supplements must immediately discontinue theiruse 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).

• Women on antiresorptive drugs (e.g. bisphosphonates) within the past year.

• Patients not capable of participating in an exercise intervention due to severe kneearthrosis or ligament/cartilage injuries of the lower extremities.

• Women with malabsorptive syndromes (i.e. cystic fibrosis, chronic pancreatitis) ortaking medications that decrease the absorption of fat soluble vitamins (i.e.Orlistat, Questran).