ERBB2 and breast cancer: T-Dxd combines trastuzumab with the topoisomerase I inhibitor deruxtecan, and its efficacy in HER2-low BC has led to its approval for use in such cases, providing a new therapeutic option for patients who previously had limited treatment choices.22 However, after a period of treatment, the patient may still develop drug resistance, necessitating a change to a new treatment regimen.