The Basal-Like Molecular Subtype of Breast Carcinoma Shows Reduced Expression for Androgen Receptor When Compared to Other Subtypes
Paul J DiMaggio, Sonal Varma, Timothy M D'Alfonso, Yi-Fang Liu, Zhengming Chen, Rachel E Kaplan, Sandra J Shin. Weill Cornell Medical College, New York, NY
Background: Androgen receptor (AR) expressing breast cancers can potentially be targeted by anti-androgens such as bicalutamide. Patients with breast cancers belonging to a particular molecular subtype may be poised to benefit more from anti-androgen therapies than those of other subtypes. We set out to investigate the prevalence of AR expression by immunohistochemistry in molecular subtypes and additionally, identify any correlation with clinicopathologic features within any single molecular subtype.
Design: Primary breast carcinomas of 573 patients were evaluated using a tissue microarray (TMA) platform. The four molecular subtypes of invasive breast carcinoma were represented as follows: Luminal A-145; Luminal B/ HER2 positive-104; Luminal B/HER2 negative and Ki-67>14%-98; Basal-like-132; HER2 enriched-94. TMA slides were immunostained with anti-AR (Novocastra) using the Bond Max Autostainer (Leica) with appropriate controls. Nuclear immunoreactivity for AR was scored using the H scoring system. Staining intensity was scored on a scale from 0 to 3 (0-negative, 1-weak, 2-moderate, 3-strong) and percentage of positive cells was recorded (0-100%). Statistical analysis (one-way ANOVA test and pairwise comparison) was performed. Within each molecular subtype, clinicopathologic variables (age, tumor type, tumor grade, tumor size, presence of lymphovascular invasion, nodal status, stage) were also correlated with AR expression.
Results: The basal-like molecular subtype showed significantly less AR expression than all other subtypes. The mean difference with (95% confidence interval) of basal-like versus Luminal A was 38.4 (16.8,60.0); Luminal B/HER2 positive 74.2 (50.3,98.2); Luminal B/HER2negative Ki-67>14% 52.5 (28.5,76.5); and HER2 enriched 33.9 (9.9,57.9). Luminal B/HER2 positive subtypes also showed significantly less AR expression than Luminal A and HER2 enriched molecular subtypes (data not shown). No clinicopathologic features were associated with AR expression in any of the molecular subtypes.
Conclusions: As a group, invasive breast carcinomas of the basal-like subtype appear least likely to benefit from anti-androgen targeted therapy than other molecular subtypes. Within any single molecular subtype, AR expression did not correlate with clinicopathologic features.
Tuesday, March 5, 2013 9:30 AM
Poster Session III # 6, Tuesday Morning