A Study of the Treatment of Disitamab Vedotin in Patients With Locally Advanced or Metastatic Pancreatic Cancer

63 patients with locally advanced or metastatic pancreatic cancer will participate in this study. HER2 expression in locally advanced or metastatic pancreatic cancer patients is defined as the expression of HER2 in tumor tissues detected by immunohistochemistry (IHC) as IHC 1+, 2+, or 3+. The arm 1 recruits 43 patients and the arm 2 recruits 20 patients.