“…Endocrine therapy (ET) with tamoxifen is the preferred adjuvant systemic therapy for ER + male BC, with demonstrated survival benefit [ 13 ]. The effectiveness of aromatase inhibitors (AIs) in this setting is less clear and this ET should not be prescribed without a gonadotropin-releasing hormone (GnRH) analogue [ 14 , 15 ]. Abemaciclib, the only approved cyclin dependent kinase 4/6 (CDK4/6) inhibitor in the adjuvant setting for ER + BC, has improved event-free survival in patients with high risk of recurrence, as per the landmark results of the MonarchE trial [ 16 ].…”