Vitamin D and Breast Cancer Epidemiologic Approach

Title: Vitamin D and Breast Cancer: An Epidemiologic Approach

Principal Investigator: Amy Millen, PhD

Funding Agency: NY State Department of Health

Period: 01/01/06 - 12/31/07

Abstract: Promising research has shown that there may be an association between reduced risk for colon and prostate cancer with increasing exposure to vitamin D. Results from cell culture and animal studies suggest that vitamin D may also protect against breast cancer, due to its ability to inhibit breast cancer cell proliferation and increase cell differentiation; there are few population studies of this possible association.

We propose to investigate associations between risk of breast cancer and exposure to vitamin D using data from the Women's Health Initiative Observational Study (WHI-OS) and the New York Exposures in Breast Cancer (WEB) Case-Control Study. Prospective associations between incident breast cancer and study center solar irradiance and region of residence, as proxy measures for an individual's vitamin D exposure, will be investigated using data from the WHI-OS. We will investigate whether or not breast cancer risk factors, measured for individuals, explain the observed associations. Risk associated with study center solar irradiance exposure will be estimated for breast cancer before and after adjustment for breast cancer risk factors, with emphasis on vitamin D intake.

The WEB study provides an important opportunity to measure associations between prevalent breast cancer and polymorphisms of the vitamin D receptor (VDR) which may alter the stability and function of the receptor and thus an individual's exposure to this vitamin at the cellular level. We will also analyze associations between breast cancer risk and vitamin D intake and major lifetime occupation using data from the WEB study.

The WEB study also has breast cancer risk factors for individuals which will be investigated as potential confounders of these associations. Both studies will provide data on associations between vitamin D exposure and development of breast cancer at a population level and are unique in that they approach the question from distinctly different angles. The WHI-OS analyses propose to investigate associations between incident breast cancer and solar and dietary vitamin D exposure. The WEB analyses propose to investigate associations between risk for breast cancer and an individual's genotype which may affect their ability to uptake vitamin D at a micro-cellular level, as well as relationships between breast cancer risk and vitamin D intake and occupation.