Predictive value of MRP2, p53, bcl2 and topoisomerase II immunostainings for the efficacy of anthracyclines-based adjuvant chemotherapy in breast cancer: Results from two randomized trials

616 Background: The identification of predictive biomarkers for the efficacy of adjuvant treatments could allow to better tailor adjuvant treatments. We evaluated the predictive value of MRP2, bcl2, topoisomerase IIα (Topo IIα) expression and p53 status for the efficacy of adjuvant anthracyclines (A)-based chemotherapy. Methods: Tumor samples from 823 patients included at Institut Gustave Roussy (IGR) in two randomized trials comparing an A-based chemotherapy with no treatment were used to perform a tissue-array. Chemotherapy consisted of 5FU (500mg/m2), farmorubicine (90% of patients) or doxorubicin (50 mg/m2) and cyclophosphamide (500 mg/m2) (D1=D28) for 6 cycles. Immunostainings (cut-off: >10% stained cells) were performed for MRP2 (M2III-6; 1:300; Alexis), p53 ( DO-7; 1:50; Dako), bcl2 (124; 1:50; Dako), and Topo IIα (KI-S1; 1:5000; Chemicon). We previously reported predictive values of ER, HER2 expression and molecular subclassification using the same tissue-array (Conforti, Annals of Oncology, 2007)...