The risk of breast cancer recurrence among patients with early-stage hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2−) disease is high, particularly among patients with lymph node-positive disease, where 1 in 6 experience recurrence or death within 5 years of initiating endocrine therapy (ET) [1]. This evidence concerns the gene ERBB2 and breast carcinoma.