Molecular breast cancer subtypes in premenopausal and postmenopausal African-American women: Age-specific prevalence and survival

Background. Breast cancer is currently regarded as a heterogeneous disease classified into various molecular subtypes using gene expression analysis. These molecular subtypes include: basal cell-like, Her-2/neu, luminal A, and luminal B. Objectives. To analyze the prevalence and clinicopathologic associations for molecular breast cancer subtypes in premenopausal and postmenopausal African-American women. Design. A retrospective analysis of all African-American women diagnosed with breast cancer from 1998 to 2005, who had assessable data for ER, PR, and Her-2/neu status. Molecular subtype classification was done based on immunohistochemical surrogates for ER, PR, and Her-2/neu status obtained from Howard University tumor registry for each patient. The molecular subtypes were defined as: luminal A (ER+ and/or PR+, HER2-), luminal B (ER+ and/or PR+, HER2+), basal-like (ER-, PR-, HER2-), and Her-2/neu (ER-, PR-, and HER2+). Outcome Measures. We analyzed the prevalence of molecular breast cancer subtypes in a population of African-American women and determined their associations with patient demographics and clinicopathologic variables: node status, tumor size, histological grade, p53 mutation status, and breast cancer-specific survival. Results. The luminal A subtype was the most prevalent in our study sample (55.4%) compared with (11.8%) luminal B, (21.2%) basal cell-like and (11.6%) Her-2/ neu subtypes. The molecular subtypes did not differ by menopausal status. However, when stratified into age-specific groups, the basal cell-like subtype (57.1%) was the most prevalent in the age group < 35 y compared with luminal A, luminal B, and Her-2/neu subtypes at 25.0%,14.3%, and 3.6%, respectively. The basal cell-like subtype also showed an age-specific bimodal distribution with a peak in the < 35 y and 51 to 65 y age groups. The basal cell-like and the Her-2/neu subtypes showed an increased association with clinicopathologic variables portending a more aggressive clinical course when compared with luminal A subtype. A paradoxical inverse relationship between the expression of p53 and Bcl-2 protooncoprotein was noted in the molecular subtypes. Breast cancer-specific survival differed significantly among the molecular subtypes (P < 0.04), with the basal cell-like and Her-2/neu subtypes having the poorest outcome. Conclusions. The high prevalence of the basal cell-like subtype in the young premenopausal African-American women aged < 35 y could be a contributory factor to the poorer prognosis of breast cancer observed in this cohort of patients. (c) 2007 Elsevier Inc. All rights reserved.