ERBB2 and gastroesophageal junction adenocarcinoma: RC48-C008 is a single-arm, open-label, multi-center phase II clinical trial of trastuzumab deruxtecan in patients with gastric/gastroesophageal junction adenocarcinoma, including those who have previously undergone ≥ 2 lines of chemotherapy for HER2 overexpression (IHC 2 + or IHC 3+).