ERBB2 and gastroesophageal junction adenocarcinoma: In 2020, the Food and Drug Administration (FDA) granted a breakthrough therapy designation to T-DXd for the treatment of patients with metastatic, HER2-mutated non-small cell lung cancer (NSCLC) after a platinum-based therapy and priority review for the treatment of HER2-positive metastatic gastric or gastroesophageal junction adenocarcinoma.