Abstract
Racial disparities in incidence and outcomes of triple-negative breast cancer (TNBC) have been attributed to ancestry, socioeconomic factors and/or obesity. We studied 253 TNBCs from 128 Black and 125 White women. Arms were balanced for age, AJCC stage, histological grade and molecular subtypes, and differed significantly in BMI distribution, obesity, and Area Deprivation Index. We examined survival rates, whole-transcriptome RNASeq and genetic ancestry. In our sample, Black race or obesity were not intrinsically predictive of poor outcomes. TNBC molecular portraits varied with stage and biological aggressiveness, irrespective of race. We identified a novel group of TNBCs with a distinctive luminal-like and stem-cell-like transcriptional profile that were equally distributed among Blacks and Whites. Genetic ancestry was highly admixed. Immune deconvolution showed a higher abundance of several immune cell populations in tumors from Blacks, which may have precision therapeutic significance, warranting further investigation of potential drivers of tumor immunity.