In 136 tamoxifen-treated patients, the 76-gene signature identified a group of patients with a poor prognosis [hazard ratio (HR), 4.62; P = 0.0248]. These patients showed a 12.3% absolute benefit of tamoxifen in 10-year DMFS (HR, 0.52; P = 0.0318) compared with untreated high-risk patients.