<h4>Objective</h4>To explore the safety and real-world efficacy of trastuzumab deruxtecan in Chinese patients with advanced breast cancer that is either HER2-positive or HER2-low expression.<h4>Methods</h4>A retrospective analysis was conducted on 104 patients diagnosed with advanced breast cancer who received trastuzumab deruxtecan treatment at the Affiliated Hospital of Xuzhou Medical University, with the study period spanning from January 2023 to September 2025. Here, ERBB2 is linked to breast cancer.