Trastuzumab Deruxtecan in HER2-Positive Breast Cancer with HER2 Loss After Dual-Target Adjuvant Therapy: A Case Report

1Department of Oncology, Zhuzhou Hospital Affiliated to Xiangya School of Medicine, Central South University, Zhuzhou, China 2Department of Medical Oncology, Shenzhen People's Hospital (The Second Clinical Medical College, Jinan University; The First Affiliated Hospital, Southern University of Science and Technology), Shenzhen, China 3Department of Nephrology, Zhuzhou Hospital Affiliated to Xiangya School of Medicine, Central South University, Zhuzhou, China The authors have no conflicts of interest to declare.