BACKGROUNDHER-2/neu overexpression appears to be associated with improved response to anthracycline-based chemotherapy, but its association with response to taxane-based chemotherapy is unclear. In this retrospective subset analysis of patients with metastatic breast cancer enrolled in a randomized treatment trial, we investigated the response of patients with known HER-2/neu status to treatment with taxane-based epirubicin-paclitaxel (ET) chemotherapy compared with treatment with epirubicin-cyclophosphamide (EC) chemotherapy.METHODSHER-2/neu status (positive [i.e., HER-2/neu amplification] or negative [i.e., no HER-2/neu amplification]) of archival specimens of primary tumors from 297 patients with metastatic breast cancer was determined by use of fluorescence in situ hybridization. Associations between HER-2/neu status and the efficacy of randomly assigned chemotherapy (ET versus EC) were investigated. All statistical tests were two-sided.RESULTSPatients with HER-2/neu-positive tumors had a statistically significantly greater objective response rate than patients with HER-2/neu-negative tumors to treatment with ET (76% versus 50%, respectively; P =.005) but not to treatment with EC (46% versus 33%; P =.130). The objective response rate associated with ET was greater than that associated with EC for both HER-2/neu-positive tumors (76% versus 46%; P =.004) and HER-2/neu-negative tumors (50% versus 33%; P =.002). However, the improvement in the objective response rate associated with ET, compared with that associated with EC, was greater for patients with HER-2/neu-positive tumors (adjusted odds ratio [OR] = 3.64, 95% confidence interval [CI] = 1.48 to 8.92; P=.005) than for patients with HER-2/neu-negative tumors (adjusted OR = 1.92, 95% CI = 1.01 to 3.64; P=.046). Among patients with HER-2/neu-positive tumors, those who received ET had better progression-free survival and overall survival than those who received EC (for progression-free survival, adjusted relative risk [RR] = 0.65, 95% CI = 0.42 to 1.02; P=.062; for overall survival, adjusted RR = 0.60, 95% CI = 0.36 to 1.02; P=.059). However, among patients with HER-2/neu-negative tumors, those who received ET and those who received EC had similar progression-free survival and overall survival.CONCLUSIONSHER-2/neu amplification does not adversely influence response to first-line chemotherapy with either ET or EC. Furthermore, a taxane-containing regimen such as ET may provide a preferential benefit to patients with HER-2/neu-positive tumors.