Radiological Complete Response as a Prognostic Marker in HR-positive Metastatic Breast Cancer Treated With CDK4/6 Inhibitors: Implications for Treatment De-escalation

rCR following CDK4/6i therapy was an independent prognostic factor in HR-positive MBC. Patients with smaller primary tumors and early administration of abemaciclib were more likely to achieve rCR. Selected patients achieving rCR may be candidates for discontinuation of CDK4/6i as part of individualized treatment de-escalation strategies.