Adjuvant abemaciclib combined with endocrine therapy for high-risk early breast cancer: updated efficacy and Ki-67 analysis from the monarchE study

Harbeck et al. 1 Harbeck N. Rastogi P. Martin M. et al. Adjuvant abemaciclib combined with endocrine therapy for high-risk early breast cancer: updated efficacy and Ki-67 analysis from the monarchE study. Ann Oncol. 2021; 32: 1571-1581 Abstract Full Text Full Text PDF PubMed Scopus (85) Google Scholar presented an update of the monarchE trial showing that the benefit of adjuvant abemaciclib is sustained beyond the 2-year treatment period. They noted that the benefit was observed regardless of Ki-67 index, and the forest plot in Figure 1B shows that treatment benefit was generally sustained across subgroups, although potentially of greater magnitude in women who were premenopausal at diagnosis. As we consider intensification of adjuvant therapy for women with HR+ breast cancer, it would be clinically useful to know whether abemaciclib benefit is independent of endocrine therapy backbone, and we would ask the authors to provide the relative and absolute benefit of the addition of abemaciclib to adjuvant therapy for premenopausal women (43% of the study population) who received first on-study endocrine therapy with tamoxifen alone without ovarian function suppression (41% of the premenopausal population) versus an aromatase inhibitor with or without ovarian function suppression. 2 Johnston S.R.D. Harbeck N. Hegg R. et al. Abemaciclib combined with endocrine therapy for the adjuvant treatment of HR+, HER2−, node-positive, high-risk, early breast cancer (monarchE). J Clin Oncol. 2020; 38: 3987-3998 Crossref PubMed Scopus (234) Google Scholar ,3 Paluch-Shimon et al. 153P Adjuvant endocrine therapy combined with abemaciclib in monarchE patients with high-risk early breast cancer: disease characteristics and endocrine therapy choice by menopausal status. Ann Oncol. 2021; 32: S427-S428 Abstract Full Text Full Text PDF Google Scholar Given the added burden of treatment escalation in terms of toxicity and health expenditures, knowing the benefit of abemaciclib specifically in high-risk premenopausal women treated with modern risk-adapted endocrine treatment would help position the drug in clinical practice.