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Cancer Epidemiol Biomarkers Prev. 2017 May;26(5):692-701. doi: 10.1158/1055-9965.EPI-16-0721. Epub 2016 Dec 8.

The Interaction between Genetic Ancestry and Breast Cancer Risk Factors among Hispanic Women: The Breast Cancer Health Disparities Study.

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Department of Biology, University of Colorado Colorado Springs, Colorado Springs, Colorado.
University of Colorado Cancer Center and Colorado School of Public Health, Aurora, Colorado.
Cancer Prevention Institute of California, Fremont, California.
Department of Health Research and Policy (Epidemiology) and Stanford Cancer Institute, Stanford University School of Medicine, Stanford, California.
Department of Medicine, Division of General Internal Medicine, Institute for Human Genetics and Helen Diller Family Comprehensive Cancer Center, University of California at San Francisco, San Francisco, California.
Department of Preventive Medicine, Keck School of Medicine of USC, Norris Comprehensive Cancer Center, University of Southern California, Los Angeles, California.
Department of Epidemiology and Population Health, School of Public Health and Information Sciences, James Graham Brown Cancer Center, University of Louisville, Louisville, Kentucky.
Moffitt Cancer Center, Cancer Prevention and Control, Tampa, Florida.
Instituto Nacional de Salud Publica, Centro de Investigacion en Salud Poblacional Av. Universidad No. 655, Col. Sta. Ma. Ahuacatitlan Cuernavaca, Morelos CP 62100, Mexico.
Department of Medicine, University of Utah, Salt Lake City, Utah.
Department of Biostatistics and Informatics, Colorado School of Public Health, Aurora, Colorado.


Background: Hispanic women have lower breast cancer incidence rates than non-Hispanic white (NHW) women. To what extent genetic versus nongenetic factors account for this difference is unknown.Methods: Using logistic regression, we evaluated the interactive influences of established risk factors and ethnicity (self-identified and identified by ancestral informative markers) on breast cancer risk among 2,326 Hispanic and 1,854 NHW postmenopausal women from the United States and Mexico in the Breast Cancer Health Disparities Study.Results: The inverse association between the percentage of Native American (NA) ancestry and breast cancer risk was only slightly attenuated after adjusting for known risk factors [lowest versus highest quartile: odds ratio (OR) =1.39, 95% confidence interval (CI) = 1.00-1.92 among U.S. Hispanics; OR = 1.92 (95% CI, 1.29-2.86) among Mexican women]. The prevalence of several risk factors, as well as the associations with certain factors and breast cancer risk, differed according to genetic admixture. For example, higher body mass index (BMI) was associated with reduced risk among women with lower NA ancestry only [BMI <25 versus >30: OR = 0.65 (95% CI, 0.44-0.98) among U.S. Hispanics; OR = 0.53 (95% CI, 0.29-0.97) among Mexicans]. The average number of risk factors among cases was inversely related to the percentage of NA ancestry.Conclusions: The lower NA ancestry groups were more likely to have the established risk factors, with the exception of BMI. Although the majority of factors were associated with risk in the expected directions among all women, BMI had an inverse association among Hispanics with lower NA ancestry.Impact: These data suggest that the established risk factors are less relevant for breast cancer development among women with more NA ancestry. Cancer Epidemiol Biomarkers Prev; 26(5); 692-701. ©2016 AACR.

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