Effects of High-Dose Vitamin D on Circulating Vitamin D Levels and Breast Density in Postmenopausal Women at High Risk for Breast Cancer Development
- Elevated risk of breast cancer defined as having at least one of the following: (1)
Predicted 5-year modified Gail model risk of 1.67% or greater, (2) Lobular carcinoma
in situ, (3) Known BRCA1 or BRCA2 deleterious mutation carrier, (4) Prior history of
ductal carcinoma in situ, if no current tamoxifen use or prior radiation to the
- Age 21 years or older.
- Postmenopausal defined as > 6 months since the last menstrual period, prior bilateral
oophrectomy, or serum FSH/LH values consistent with institutional normal values for
the postmenopausal state.
- Baseline mammographic density ≥25% as assessed qualitatively by the mammographer
(25-50% = "scattered fibroglandular densities"; >50-75% = "heterogeneously dense
breasts"; >75% = "extremely dense breasts").
- Baseline serum 25-hydroxyvitamin D <32 ng/ml.
- Normal breast exam and mammogram (BIRADS score of 1 or 2).
- Prior tamoxifen or raloxifene use is allowed provided treatment is discontinued at
least 28 days prior to enrollment.
- At least one breast available for imaging. No bilateral breast implants.
- Willingness to not take vitamin D supplements during the one year intervention, but
up to 1000mg of calcium supplementation is allowed.
- Normal serum calcium.
- No history of kidney stones.
- Adequate renal and hepatic function: serum creatinine, bilirubin, AST, ALT and
alkaline phosphatase < 2.0 x the institutional upper limit of normal (IULN).
- No hypersensitivity reactions to vitamin D.
- Zubrod performance status of 0 or 1.
- Not on estrogen replacement therapy.
- No significant medical or psychiatric condition that would preclude study completion.