Ethnic disparities in breast tumor phenotypic subtypes in Hispanic and non-Hispanic white women

Hispanic women are at a lower risk of getting breast cancer than non-Hispanic white (NHW) women, yet they experience a higher risk of mortality after diagnosis. There is some evidence to suggest differences in tumor pathology; however, very limited research has been published on Hispanic women. This represents one of the first studies to evaluate the prevalence of tumor markers and phenotypic subtypes that are associated with poorer prognosis (human epidermal growth factor receptor 2 [HER2], triple negative and basal-like tumors) among Hispanic women.

We reviewed pathology reports, obtained paraffin blocks of breast cancer tissue, and established tissue microarrays from NHW (n=119) and Hispanic women (n=69) who were Colorado participants in the 4-Corners Breast Cancer Study. We evaluated ethnic differences in the prevalence of tumor markers and phenotypic subtypes and assessed the contribution of risk factors in explaining the observed differences.

Consistent with other studies, Hispanic women had a higher prevalence of estrogen receptor-negative tumors compared with NHWs (36.2% vs. 22.7%, p=0.05). Hispanics also had an unexpectedly higher proportion of HER2-positive tumors compared with NHWs (31.9% vs. 14.3%, p<0.01). Independent of other prognostic factors, Hispanics were 2.8 times more likely to have a HER2-positive tumor (95% confidence interval [CI] 0.98-7.86). Hispanics were less likely to have the more favorable luminal A subtype, but no significant differences were observed for the less favorable basal-like or triple negative subtypes. However, there were suggestive differences when considering menopausal status.

These findings provide evidence that breast cancers among Hispanic women comprise a distinct spectrum of tumor subtypes when compared with NHW women.