ERBB2 and breast cancer: In May 2022, the breast cancer indication for T-DXd was expanded in the USA to include use in adult patients with unresectable or metastatic HER2-positive breast cancer who received treatment with a prior anti-HER2-based regimen in the metastatic setting or in the neoadjuvant or adjuvant setting and who developed disease recurrence during or within 6 months of completing therapy.11