Sunlight reduces risk of breast Ca

Exposure to sunlight lowers the risk of advanced breast cancer among light-skinned women, according to a report published online Oct. 12 in the American Journal of Epidemiology.

Esther M. John, PhD, of the Stanford University School of Medicine in Stanford, Calif., and colleagues interviewed and measured skin pigmentation of 1,788 newly diagnosed breast cancer patients between 1995 and 2003. Subjects included blacks, Hispanics, and non-Hispanic whites between the ages of 35 and 79. They were matched with 2,129 controls. Biospecimens were taken on a subset of both groups to examine polymorphisms in the vitamin D receptor gene.

The researchers found that sun exposure lowered the risk of advanced breast cancer (but not localized breast cancer) in women with light complexions; the risk in women with the lightest complexions was reduced by 47%. This association was not modified by genotype of the vitamin D receptor gene. No association between sunlight exposure and breast cancer risk was observed for medium- or dark-skinned women.

"If confirmed by other studies, our finding of a decreased risk for advanced but not localized breast cancer cases has significant public health implications," the authors conclude. "In particular, if sun exposure reduces the risk of tumor progression, vitamin D could be recommended for women diagnosed with localized breast cancer."

John EM, Schwartz GG, Koo J, et al. Sun exposure, vitamin D receptor gene polymorphisms, and breast cancer risk in a multiethnic population. Am J Epidemiol. 2007;166:1409-1410; doi:10.1093/aje/kwm259 (published online 12 October 2007).