Impact of HER2-low expression on the efficacy of endocrine therapy with or without CDK4/6 inhibitor in HR-positive/HER2-negative metastatic breast cancer: A prospective study.

This study suggested that HER2-low expression may predict the efficacy of ET but not that of CDK4/6 inhibitor plus ET in HR-positive/HER2-negative MBC patients. The results of this study highlight the importance of integrating HER2 status in tailoring personalized treatment strategies for HR-positive MBC.