Conditions: Breast Cancer
Keywords: breast cancer chemoprevention vitamin D breast density
Allocation: RANDOMIZED | Intervention model: PARALLEL
Enrollment: 20
Healthy volunteers: yes

Brief summary:
This is a phase II study which will enroll 20 postmenopausal women who are at high risk for breast cancer development. The goal is to determine whether a one-year intervention of high-dose vitamin D at 2 different doses (20,000 IU weekly or 30,000 IU weekly) will increase circulating blood levels of vitamin D and to obtain preliminary data on the biologic effects of vitamin D for breast cancer prevention.

Detailed description:
Participants will receive oral vitamin D3, cholecalciferol 20,000 IU or 30,000 IU weekly. Before beginning the intervention, the participants will have a general physical exam including a clinical breast exam and anthropometric measures, a morning blood draw (for analysis of 25(OH)D, 1,25(OH)D, parathyroid hormone (PTH), insulin-like growth factor (IGF)-I, insulin-like growth factor-binding protein 3 (IGFBP-3), estradiol, estrone, testosterone, and sex hormone-binding globulin (SHBG) at baseline, 6 months, and 12 months) and a bilateral mammogram (at baseline and 12 months). Participants will also complete a baseline questionnaire, collecting data on demographic information and breast cancer risk factors. In addition, we will be collecting data on vitamin D sources from diet and sunlight exposure using a validated questionnaire administered at baseline and 12 months.

For follow-up visits, the participant will be seen at the study site at months 3, 6, 9, and 12. During these visits, drug will be dispensed, adherence ascertained, and adverse events will also be assessed. In addition, blood (serum calcium, albumin, creatinine) and urine (urine calcium, creatinine) will be collected to monitor for toxicity. A 24-hour urine collection will be conducted at baseline and 12 months to assess for hypercalciuria. After the 1 year intervention, all participants will have a complete physical exam including clinical breast exam, a bilateral mammogram, blood draw, and complete a follow-up questionnaire.

Arms:
arm 1: Postmenopausal women who are at increased risk for breast cancer development receiving vitamin D3, oral cholecalciferol 20,000 IU weekly, for one year.

Cholecalciferol 20,000 IU (2 active capsules + 1 matching placebo capsule) arm 2: Postmenopausal women who are at increased risk for breast cancer development receiving vitamin D3, oral cholecalciferol 30,000 IU weekly, for one year.

Cholecalciferol 30,000 IU (3 active capsules)

Interventions: intervention 1: Cholecalciferol intervention 2: Placebo capsule
Intervention descriptions: intervention 1: Cholecalciferol is a vitamin D3. Vitamin D is important for the absorption of calcium from the stomach and for the functioning of calcium in the body. Cholecalciferol is used to treat or prevent many conditions caused by a lack of vitamin D.

Cholecalciferol will be available in gel capsule form at 10,000 IU (0.25 mg cholecalciferol) each. intervention 2: Matching placebo capsules

Protocol document: