European origin may up Latinas' breast cancer risk

NEW YORK (Reuters Health) - Among United States Latinas, a greater degree of European genetic ancestry is associated with an increased risk of breast cancer, the results of a new study indicate. This could be due to environmental factors, genetic factors, or the interplay of the two, the study team suggests.

Latina women generally have a lower risk of breast cancer compared with European, African-American or non-Latina white women do, according to the report, which published in Cancer Research. This is partially explained by differences in the number of known risk factors; but genetics may also be involved.

Latinas are a group originating from genetically divergent populations, mostly Europeans and Indigenous Americans, note Dr. Laura Fejerman of the University of California, San Francisco, and colleagues. In their study, the researchers evaluated the genetic ancestry of 440 Latinas with breast cancer and 597 Latinas without breast cancer.

They found that those with more European ancestry had an increased risk of breast cancer. For example, women with 25 percent more European ancestry than the average were nearly 80 percent more likely to develop breast cancer.

The "most important result," Fejerman told Reuters Health, is that even after accounting for the contribution of many known risk factors for breast cancer, the association between increased risk and higher levels of European genetic ancestry was still statistically significant, at 39 percent.

This finding might be attributable "to the effect of non-genetic risk factors that correlate with genetic ancestry and that we did not know about, or to the effect of one or more genetic variants that might act on their own or in interaction with non-genetic factors," Fejerman said.

The next step will be to "try to find those genetic variants," she added, "since finding them would be the only way to confirm that the increase in breast cancer risk in Latinas with higher European ancestry is due to genetic factors."

The results "should also encourage researchers to understand better the different lifestyle decisions and other environmental exposures of the Hispanic population in the U.S. to evaluate why a higher European genetic component would increase a woman's chance of developing breast cancer," Fejerman concluded.

The study was funded by the National Cancer Institute and the Department of Defense Breast Cancer Research Program.

SOURCE: Cancer Research, December 1, 2008.