ERBB2 and breast cancer: In 2022, based on the results of the DESTINY-Breast03 trial [63], T-DXd was also approved as a second-line treatment for patients with unresectable or metastatic HER2-positive breast cancer who have received a prior anti-HER2-based regimen either in the metastatic setting or in the neoadjuvant or adjuvant setting and have developed disease recurrence during or within six months of completing therapy.