ERBB2 and breast carcinoma: HR-positive, HER2-negative, node-negative patients with breast cancer defined by diagnosis: before RS funding (cohort 1 [C1]: January 2013–December 2013), after introduction of public RS funding (cohort 2 [C2]: July 2015–June 2016), and after TAILORx results (cohort 3 [C3]: July 2018–June 2019). Patients aged 18–80 years with stage I–III breast cancer. Cohort 1 median age (SD): 62(23–80), Cohort 2: 62(21–80), Cohort 3 61(28–80).