Marin County’s High Breast Cancer Rate May be Tied to Genes

Dr. Kathie Dalessandri

By Jason Bardi,
Courtesy of UCSF

Marin County, has one of the highest rates of breast cancer in the world, a fact that scientists know has nothing to do with the land itself but with some other, unknown factor.
A new study that analyzed mouth buccal cell samples stored frozen at UC San Francisco (UCSF) suggests what this factor may be: a genetic trait present among women within the county’s predominantly white population.
In an article published online by the Journal of the American College of Surgeons, which will appear in the November 2012 print issue, surgeon scientist Dr. Kathie Dalessandri, colleagues at UCSF and the company InterGenetics Inc. in Oklahoma City, describe how, in a small, retrospective pilot study involving the mouth cells from 338 women living in Marin, slight variations within the DNA of a human gene for vitamin D receptor were associated with breast cancer risk.
“While the findings must be validated in a much larger, prospective study,” Dalessandri warned, “we found that women who were at high risk for breast cancer were 1.9 times more likely to have a specific vitamin D receptor variation than the general population.”
A larger, collaborative prospective study in Marin County is ongoing, spearheaded by the Marin County Department of Health and Human Services. This study includes an examination of breast cancer risk on a scale involving thousands of women.
For now, Dr. Dalessandri said, there is no clear-cut advice on the level of vitamin D needed for breast cancer prevention, but variations in the Vitamin D receptor may be an important modulator of risk.
The discovery does not rule out that there may be other factors involved in the elevated breast cancer risk in Marin County, said Dalessandri, but it gives an important clue moving forward.