ESR1 and breast cancer: In another retrospective study of 112 postmenopausal women with stages I–IIIB ER+ early breast cancer before and after 2-weeks' anastrozole treatment in a neoadjuvant trial, patients with HER2-E subtype (n = 9 [8.0%]) or Basal-like subtype (n = 3 [2.7%]) showed a poorer Ki67 response (mean Ki-67 change of−50.7 and +15.3%) compared to Luminal A or B subtypes (mean Ki-67 change of−75%).