African American women with breast cancer may have more aggressive tumor biology compared to white women through greater intratumor genetic heterogeneity and more basal gene expression tumors, according to a recent study published online ahead of print in the Journal of Clinical Oncology.1

Researchers led by Tanya Keenan, MD, of the Massachusetts General Hospital in Boston, looked at exome sequencing in 663 white and 105 African American women, as well as gene expression data in 711 white and 159 African American women who were diagnosed with stage 1 to 3 breast cancer from 1988 to 2013.

They found that African American women had more TP53 mutations and fewer PIK3CA mutations. Additionally, intratumor genetic heterogeneity was greater in African American than white tumors by 5.1 units, and within triple-negative tumors by 4.1 units.

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Using the predication analysis of microarray method, they found that African American women had more basal tumors by the 50-gene set predictor, as well as fewer PAM50 luminal A tumors.

In triple-negative subtypes, African Americans were found to have more basal-like 1 and mesenchymal stem-like tumors, as well as a higher risk of tumor recurrence than whites.

The authors concluded that differences in TP53 mutation, PAM50 basal subtype, and triple-negative tumor prevalence may “contribute to racial disparity in breast cancer outcomes.”


  1. Keenan T, Moy B, Mroz EA, et al. Comparison of the genomic landscape between primary breast cancer in African American versus white women and the association of racial differences with tumor recurrence. [published online ahead of print September 14, 2015].J Clin Oncol. doi: 10.1200/JCO.2015.62.2126.