European Ancestry May Raise Breast Cancer Risk in US Latinas

By Megan Rauscher

NEW YORK DEC 04, 2008 (Reuters Health) - Among US Latinas, a greater degree of European genetic ancestry is associated with increased breast cancer risk, results of a study indicate. This could be due to environmental factors, genetic factors, or the interplay of the two, the study team says.

In general, Latina women have a lower risk of breast cancer than European, African-American, or non-Latina White women, they explain in the December 1 issue of Cancer Research. This is partially explained by differences in the prevalence of known risk factors, but genetics may also be involved.

"Latinas are an admixed population with most of their genetic ancestry from Europeans and Indigenous Americans," note Dr. Laura Fejerman of the University of California, San Francisco, and colleagues. In their study, the researchers studied the genetic ancestry of 440 Latina women with breast cancer and 597 Latina women without breast cancer.

They found that higher European ancestry was associated with increased breast cancer risk. The odds ratio associated with a 25% increase in European ancestry was 1.79 (p < 0.001).

"The most important result," Dr. Fejerman told Reuters Health, "is that even after adjusting for multiple previously described risk factors for breast cancer, the association between high European genetic ancestry and increased breast cancer risk is still significant (odds ratio, 1.39) in the sample of US Latinas studied."

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," Dr. Fejerman said.

"The next obvious step," she continued, "is to try to find those genetic variants, 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 US to evaluate why a higher European genetic component would increase a woman"s chance of developing breast cancer," Dr. Fejerman concluded.

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

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