Molecular breast cancer subtypes in premenopausal African-American women, tumor biologic factors and clinical outcome.

INTRODUCTION: Breast cancer is currently viewed as a heterogeneous disease made up of various subtypes, with distinct differences in prognosis. Our goal was to study the distribution and to characterize the clinical and biological factors that influence the behavior and clinical management of the different molecular breast cancer subtypes in premenopausal African-American women.

METHODS: A retrospective analysis of Howard University Hospital tumor registry, for all premenopausal African-American women aged less than 50 years, diagnosed with breast cancer from 1998-2005, was performed.

RESULTS: The luminal A subtype was the most prevalent (50.0%), vs basal-cell-like (23.2%), luminal B (14.1%), and HER-2/neu (12.7%). However when stratified by age groups, results showed that in the age group <35 years the basal-cell-like subtype was the most prevalent (55.6%), vs 25.9%, 14.8%, and 5.6% for luminal A, luminal B, and HER-2/neu subtypes, respectively (P < .000). P53 mutation was more prevalent in the basal-cell-like subtype compared to luminal A (48.0% vs 18.6%, P < .01). The expression of the Bcl-2 gene differed by subtype, with the luminal A and luminal B subtypes more likely to overexpress the Bcl-2 gene (89.1% luminal A, 80.0% luminal B vs 47.6% basal-cell-like and 40.0% HER-2/neu, P < .000). Though not statistically significant, HER-2/neu and basal-cell-like subtypes had the shortest survival time (P < .31).

CONCLUSION: The high prevalence of the basal-cell-like subtype in young premenopausal African-American women aged <35 years may contribute to the poorer prognosis observed in this cohort of African-American women.