ERBB2 and aneurysmal bone cyst: MONARCH 2 examined abemaciclib in combination with fulvestrant in patients with HR+, HER2− ABC who had progressed on prior ET and who were of any menopausal status, representing a younger patient population (median age [minimum–maximum]: 58.0 [32–81] years) [13] compared with the MONARCH 3 subpopulation (64.0 [47–75] years).