Current and Upcoming Treatment Strategies After CDK4/6 Inhibitors for Patients With ER+/HER2- Advanced Breast Cancer

Abstract

This industry symposium took place during the 2023 European Society for Medical Oncology (ESMO) Congress in Madrid, Spain, with a goal of presenting the latest recommendations and upcoming treatment strategies for patients with oestrogen-receptor positive (ER+), human epidermal growth factor receptor 2 negative (HER2-) advanced breast cancer, who experience disease progression after cyclin-dependent kinase 4/6 (CDK4/6) inhibitors. An expert panel of clinicians explained that most patients will eventually develop resistance to endocrine therapy during the metastatic setting, and there remains a considerable margin for improvement in the second-line (2L) treatment of these patients. Data for current therapeutic options in this patient population were presented, showing that patients who have previously received CDK4/6 inhibitor therapy are often resistant to many of the available 2L therapies, including combination therapies, and that resistance appears during first-line (1L) treatment, becoming particularly significant in tumours harbouring ERS1 mutations. The recent approval of the oral selective oestrogen receptor degrader (SERD), elacestrant, was also discussed. The supporting data for this monotherapy at 2L was presented, along with changes made to the U.S. Food and Drug Administration (FDA) and European Union (EU) best practice recommendations to accommodate this therapeutic option. The panel stressed the importance of testing for ESR1 mutations at each progression during the metastatic treatment course, which is particularly relevant following the approval of elacestrant, for which ESR1 mutation is a predictive factor for efficacy.