Gene expression-based predictors of chemotherapy response in basal-like breast cancer.

10500 Background: The Basal-like subtype is generally associated with high chemo-sensitivity, but not all tumors respond and/or benefit to the same extend. In this study, we sought to identify gene expression predictors of neoadjuvant chemotherapy sensitivity in Basal-like breast cancer. Methods: Expression of 542 genes was measured using the Nanostring nCounter platform from 69 FFPE pre-treated samples of the GEICAM/2006-03 phase II trial, which were treated with epirrubicin/cyclophosphamide followed by docetaxel+/- carboplatin. Research-based PAM50 and Claudin-low predictors were also evaluated. The association between response (Miller-Payne criteria) and gene/signatureexpression was assessed by multivariable ordinal logistic regression. Significant findings were evaluated in 109 independent triple-negative and Basal-like tumors treated with anthracycline/ taxane-based chemotherapy (Hatzis et al.). Finally, interaction tests were performed to identify genes/signaturesassociated with carboplatinresponse...