European Ancestry Increases Breast Cancer Risk Among Latinas

"We need to study the possible factors that are placing Latina women of high European ancestry at greater risk," said Laura Fejerman, Ph.D., a post-doctoral research fellow at the University of California San Francisco. "The increased risk could be due to environmental factors, genetic factors or the interplay of the two."

Latinas are what geneticists refer to as an "admixed" population with most of their genetic ancestry from European or indigenous Americans. Fejerman said the term "indigenous Americans" usually refers to the groups that lived on the American continent prior to the arrival of the European colonizers.

For the current study, Fejerman and colleagues identified the genetic ancestry of 440 Latina women with breast cancer and 597 Latina women who did not have breast cancer.

For every 25 percent increase in European ancestry there is a 79 percent increase in the risk of breast cancer. If a woman had an estimated European ancestry of 25 percent she would be 79 percent more likely to have breast cancer than a woman of full indigenous American ancestry.

After accounting for known risk factors like number of full-term pregnancies or months of breastfeeding, the breast cancer risk for every 25 percent increase in European ancestry decreased to 39 percent, but it remained statistically significant.

Fejerman said that the overall risk of Latinas in the US is less than in European Americans but higher than indigenous Americans. She said further research would need to be conducted to determine if these differences are due to the presence of non-genetic risk factors that have not yet been described and that vary with ancestry, to the effect of genetic variants that either are protective or increase risk, or the result of the interaction between genes and non-genetic factors.