DESTINY-Breast 04, a phase III trial that included patients with BM, compared T-DXd vs. the treatment of physician’s choice (TPC) in previously treated HER2-low advanced breast cancer and showed that patients treated with T-DXd presented significantly longer PFS and OS than the TPC group (23.9 vs. 17.5 months; p = 0.003) [66]. This evidence concerns the gene ERBB2 and breast cancer.