Topoisomerase IIα Gene Amplification Predicts Favorable Treatment Response to Tailored and Dose-Escalated Anthracycline-Based Adjuvant Chemotherapy in HER-2/neu–Amplified Breast Cancer: Scandinavian Breast Group Trial 9401

Purpose Amplification of the HER-2/neu and topoisomerase IIα (TOP2A) genes has been linked to the effects of anthracyclines. Their role in predicting the outcome of anthracycline-based adjuvant chemotherapy for breast cancer patients has remained controversial. Patients and Methods The present substudy of the Scandinavian Breast Group trial 9401, in which an epirubicin-based regimen (nine courses of tailored and dose-escalated fluorouracil, epirubicin, and cyclophosphamide [FEC]) was compared with three or four courses of standard FEC followed by bone marrow–supported high-dose chemotherapy (cyclophosphamide, thiotepa, and carboplatin), included high-risk breast cancer patients (with eight or more positive axillary lymph nodes or at least five nodes with additional poor prognostic indicators). Amplification of HER-2/neu was determined retrospectively in paraffin-embedded tumor tissue sections by chromogenic in situ hybridization. TOP2A was tested only in HER-2/neu–amplified tumors. Results HER-2/neu amplification alone, which was present in 32.7% of the tumors, was a strong prognostic factor for short relapse-free (P = .0034) and overall survival (P = .0008) but showed no direct association with treatment assignment. TOP2A coamplification, which was present in 37% of HER-2/neu–amplified tumors, was associated with better relapse-free survival in patients treated with tailored and dose-escalated FEC (hazard ratio [HR] = 0.45; P = .049). A statistical multivariate Cox's regression analysis confirmed the predictive significance of TOP2A coamplification (HR = 0.30; P = .020) in HER-2/neu–amplified tumors. There was no such association in patients with HER-2/neu–amplified tumors without TOP2A gene amplification. Conclusion Coamplification of HER-2/neu and TOP2A may define a subgroup of high-risk breast cancer patients who benefit from individually tailored and dose-escalated adjuvant anthracyclines.