RecruitingDrug trialReal-world Effectiveness and Safety of Trastuzumab Deruxtecan in Patients With Locally Advanced or Metastatic HER2-positive Gastric or Gastroesophageal Junction Adenocarcinoma in ChinaTrastuzumab deruxtecan's (T-DXd's) efficacy and safety has been confirmed in traditional clinical trials, there is a lack of real-world evidence, especially among Chinese patients. The objective of this study is to evaluate real-world effectiveness and safety profile of T-DXd by collecting real-world data treating in patients with locally advanced or metastatic HER2-positive gastric or gastroesophageal junction adenocarcinoma.