• Hasan Cagri Yildirim, Mustafa Buyukkor, Gözde Kavgaci, Buket Şahin Celik, Kadriye Bir Yucel, Bengü Dursun, Elvin Chalabiyev, Funda Yilmaz, Saadet Sim Yildirim, Fatih Kus, Fatih Tay, Asli Gecgel, Bariş Koksal, Deniz Can Guven, Ozan Yazici, Yüksel Urun, Ahmet Ozet, Erhan Gokmen, Berna Oksuzoglu, and Sercan Aksoy.
• Department of Internal Medicine, Division of Medical Oncology, Faculty of Medicine, Hacettepe University, Ankara, Turkey.
• Medicine (Baltimore). 2024 Jul 26; 103 (30): e38828e38828.

AbstractThe fact that the human epidermal growth factor receptor 2 (HER2)-low group, historically classified as HER2 negative in breast cancer histology, benefited from HER2-targeted treatments similarly to the HER2-positive group indicates that this group has a distinct histology from the HER2-0 group. The effectiveness of cyclin-dependent kinase 4/6 inhibitors, which are the standard first-line treatment for hormone receptor-positive, HER2-negative advanced breast cancer, in this newly defined histological subgroup remains a topic of debate. In our study, we examined the impact of HER2 status on the efficacy of CDK4/6 inhibitors. Our study is a retrospective, multicenter, real-world data analysis. One hundred sixty patients were included in the study. The relationship between HER2 status and other clinical-pathological features, as well as progression-free survival, was examined. Median follow-up was 20.33 ± 0.98 months. The mPFS could not be reached. All patients exhibited positive estrogen receptor expression. Among the patients, 111 (69.4%) were categorized as HER2-0, and 49 (30.6%) as HER2-low. The 24-month progression-free survival rates were similar between HER2-0 and HER2-low patients (60.6% vs 65.3%, hormone receptor: 1.18, CI: 0.67-2.20, P = .554). We established that the mPFS achieved with cyclin-dependent kinase 4/6 inhibitors as a first-line therapy for patients with advanced breast cancer is unaffected by HER2 status.Copyright © 2024 the Author(s). Published by Wolters Kluwer Health, Inc.

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