DAISY was a phase 2 trial in which 179 patients with heavily pretreated advanced breast cancer were treated with T-DXd; the study included 68 patients with HER2 3+ breast cancer, 73 with HER2-low breast cancer, and 38 with HER2-null breast cancer (IHC 0) [102]. This evidence concerns the gene ERBB2 and breast carcinoma.