ERBB2 and gastroesophageal junction adenocarcinoma: In addition to breast cancer, T-DXd is also approved for HER2-mutant non-small-cell lung cancer, HER2-positive gastric or gastroesophageal junction adenocarcinoma, and any unresectable or metastatic HER2-positive (IHC 3 +) solid tumors [8–10].