Clinicopathological Characteristics of Patients with HR-Positive/HER2-Negative Metastatic Breast Cancer Experiencing Early Progression Within 6 Months of CDK4/6 Inhibitor Therapy
Okan Aydın1, Gülhan Dinç1, Şermin Dinç Sonuşen1, Ahmet Emin Öztürk1, Mert Erciyestepe1, Ömer Burak Ekinci1, Zehra Sucuoğlu İşleyen1, Kayhan Ertürk11Department of Medical Oncology, University of Health Sciences, Prof. Dr. Cemil Taşcıoğlu City Hospital, İstanbul, Türkiye
Objectives: To investigate the clinicopathological characteristics of patients with hormone receptor (HR)-positive/human epidermal growth factor receptor 2 (HER2)-negative metastatic breast cancer who experienced early progression during first-line CDK4/6 inhibitor therapy and to identify factors associated with ultra-early progression. Methods: This retrospective, single-center study included patients with radiologically confirmed disease progression within 6 months of first-line CDK4/6 inhibitor-based therapy between 2020 and 2025. Patients progressing within 3 months were classified as ultra-early progressors, whereas those progressing between 3 and 6 months served as the reference group. Clinicopathological features, treatment characteristics, and survival outcomes were analyzed. Logistic regression was performed to identify factors associated with ultra-early progression. Results: Among 418 treated patients, 55 (13.2%) developed early progression; 26 (47.3%) progressed within 3 months and 29 (52.7%) between 3 and 6 months. Liver metastasis was significantly more common in ultra-early progressors (57.7% vs. 31.0%, p=0.047) and showed a trend toward an independent association with ultra-early progression (OR 3.05, 95% CI 0.99–9.44, p=0.053). No significant association was observed between MCV changes or progression timing and overall survival. Conclusion: Liver metastasis may identify patients at increased risk of ultra-early progression during first-line CDK4/6 inhibitor therapy and may facilitate early risk stratification. Keywords: CDK4/6 inhibitors, Early progression, Metastatic breast cancer
Cite This Article
Aydın O, Dinç G, Dinç Sonuşen Ş, Öztürk A, Erciyestepe M, Ekinci Ö, Sucuoğlu İşleyen Z, Ertürk K. Clinicopathological Characteristics of Patients with HR-Positive/HER2-Negative Metastatic Breast Cancer Experiencing Early Progression Within 6 Months of CDK4/6 Inhibitor Therapy. EJMI. 2026; 10(3): 433-440
Corresponding Author: Okan Aydın