In TAILORx, which included 9719 eligible patients with node-negative HR + HER2‒ early-stage BC, patients with Recurrence Score® (RS) results 11–25 were randomized to CT plus endocrine therapy (ET) vs ET alone, whereas all patients with RS 0–10 results received ET alone and all patients with RS 26–100 results received CT plus ET2. This evidence concerns the gene ERBB2 and breast cancer.