TDXd has demonstrated impressive efficacy in the context of HER2-positive (HER2+) and HER2-low breast cancers [2,3,4,5,6,7], including in patients with central nervous system (CNS) metastases [8,9,10,11,12,13], as well as with other HER2-expressing or mutated tumor types [14,15,16,17,18,19,20,21,22,23]. This evidence concerns the gene ERBB2 and breast cancer.