Clinical Efficacy and Security Analysis of CDK4/6 Inhibitors Combined with ET in Patients with HR+HER2− Advanced Breast Cancer

Yan Wang,1,* Dongmei Chen,2,* Zhenning Wang,3 Xiaoye Jin,4 Jiao Zhang,1 Ye Lv1 1Department of Medical Oncology III, General Hospital of Ningxia Medical University, Yinchuan, 750004, People’s Republic of China; 2Department of Oncology, Anhui Chest Hospital, Hefei, Anhui, People’s Republic of China; 3Department of Breast Surgery, Yinchuan Maternal and Child Health Hospital, Yinchuan, 750004, People’s Republic of China; 4Ningxia Medical University, Yinchuan, 750004, People’s Republic of China*These authors contributed equally to this workCorrespondence: Jiao Zhang, Department of Medical Oncology III, General Hospital of Ningxia Medical University, No. 804, Shengli Street, Xingqing District, Yinchuan, Ningxia Hui Autonomous Region, People’s Republic of China, Email [email protected] Ye Lv, Department of Medical Oncology III, General Hospital of Ningxia Medical University, No. 804, Shengli Street, Xingqing District, Yinchuan, Ningxia Hui Autonomous Region, People’s Republic of China, Email [email protected]: To evaluate the clinical efficacy and security of CDK4/6 inhibitors (CDK4/6i) combined with endocrine therapy (ET) in patients with hormone receptor-positive (HR⁺), human epidermal growth factor receptor 2-negative (HER2−) advanced breast cancer.Methods: We selected 145 patients with HR+HER2− advanced breast cancer from the hospital’s electronic medical record system and divided them into an observation group of 83 cases (CDK4/6i combined with ET treatment) and a comparison group of 62 cases (ET treatment) according to the treatment plan. Analyze and compare the efficacy and security of patients receiving different treatment regimens.Results: The ORR was significantly higher in the observation group (CDK4/6i + ET) compared to the comparison group (ET alone) (45.8% vs. 22.6%, p=0.005). The DCR was also superior in the observation group (84.3% vs. 67.7%, p=0.018). The median PFS was 15.0 months (95% CI: 12.5– 17.5) in the observation group versus 9.0 months (95% CI: 7.5– 10.5) in the comparison group (p< 0.001). The median OS was 20.5 months (95% CI: 18.0– 23.0) and 9.5 months (95% CI: 8.0– 11.0), respectively (p=0.002). COX multivariate analysis identified ER level as an independent protective factor (HR=0.559, 95% CI: 0.352– 0.888, p< 0.05), while liver metastasis was an independent risk factor for PFS.Conclusion: CDK4/6 inhibitors combined with ET demonstrates favorable clinical efficacy in patients with HR⁺HER2− advanced breast cancer, with manageable adverse reactions and a good security profile. The ER level may be an independent protective factor affecting the PFS of the overall population, while liver metastasis may be an independent risk factor affecting the PFS of patients.Keywords: breast cancer, cdk4/6 inhibitor, endocrine therapy, hormone receptor positive, the epidermal growth factor receptor