African American (AA) women have higher mortality from breast cancer (BC) compared to European American (EA) women. This may be due to the higher proportion of AA women with tumors that are diagnosed at advanced stage and are estrogen receptor negative (ER-) /progesterone receptor negative (PR-). Our study sought to determine whether self-reported race and percent African ancestry were associated with BC tumor characteristics. In a multi-center, population-based case-control study of BC, we determined percent African ancestry using ancestry informative markers (AIM) among women self-reporting as Black. While self-reported race was associated with several BC tumor characteristics, AIMs markers among AA women were not. Specifically, women self-reporting as Black were at a 30% reduction in ER+/PR+ tumors (95% CI: 0.6–0.9), a non-significant risk of ER-/PR-tumors (OR = 1.3 [95% CI: 0.9–1.7]), a 1.4-fold increased risk of regional/distant stage (95% CI: 1.1–1.7) and a 1.5-fold increased risk of high grade tumors (95% CI: 1.2–1.9) compared to EA women. Percent African ancestry was not associated with any BC tumor characteristics (OR=1.0 for ER+/PR+ [95% CI: 0.6–1.8], OR = 0.9 for ER-/PR-[95% CI: 0.5–1.6], OR = 1.3 for regional/distant stage [95% CI: 0.8–2.1], and OR=0.9 for high-grade tumors [95% CI: 0.6–1.4] comparing those with ≥95% African ancestry to those with <80% African ancestry). This analysis suggests that factors unrelated to AA women's genetic ancestry contribute to racial differences in BC tumor characteristics.

Citation Information: Cancer Epidemiol Biomarkers Prev 2011;20(10 Suppl):A89.

Copyright © September 18, 2011, American Association for Cancer Research
2011