CDK4 and breast cancer: The EMERALD clinical trial (NCT03778931) (Study Details Phase 3 Trial of Elacestrant vs Standard of Care for the Treatment of Patients With ER+/HER2- Advanced Breast Cancer ClinicalTrials.gov, 2023)compared elacestrant with endocrine therapy in patients with ER+/HER2-advanced or metastatic breast cancer who had disease progression after CDK4/6 inhibitor therapy.