Im SA, et al. - Through another phase 3 trial on 672 patients in premenopausal or perimenopausal stage with advanced hormone-receptor–positive and human epidermal growth factor receptor 2 (HER2)–negative breast cancer, the contributors targetted to understand the benefits of addition of a cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitor to endocrine therapy for progression-free survival than endocrine therapy alone. Overall survival with a CDK4/6 inhibitor and endocrine therapy in comparison with endocrine therapy alone, in patients with advanced hormone-receptor–positive, HER2-negative breast cancer was significantly longer. No toxic effects with longer follow-up have emerged.