T-DXd has demonstrated superior efficacy not only in HER2-positive breast cancers [21,22] but also in HER2-low (IHC 1+ or IHC 2+/ISH-non-positive) advanced breast cancers [23] and HER2-mutant non-small-cell lung cancers [24]. The gene discussed is ERBB2; the disease is non-small cell lung carcinoma.