Progression-free survival of 23 months with second-line trastuzumab deruxtecan in HER2-positive gastroesophageal junction adenocarcinoma: a case report

Introduction Trastuzumab deruxtecan (T-DXd) has been approved for the second-line therapy of human epidermal growth factor receptor 2 (HER2)-positive advanced gastric cancer, revolutionizing the treatment landscape for this clinical scenario. Case Presentation Given the lack of real-world evidence, here we reported a patient with HER2-positive, metastatic gastroesophageal junction adenocarcinoma treated with T-DXd in the second-line setting. The patient, a 63-year-old male, previously received first-line treatment with trastuzumab plus oxaliplatin, capecitabine and sintilimab but disease progression occurred at 4.5 months. He subsequently received T-DXd-based therapy for a total of 22 treatment cycles and achieved a progression-free survival (PFS) of 23 months, with improved performance status and no T-DXd treatment dose reduction during treatment. Conclusion This case firstly supplements the real-world data of T-DXd for patients with HER2-positive advanced gastric cancer in the second-line setting. These data indicate the PFS benefit with second-line T-DXd-based treatment even after rapid progression on trastuzumab-based therapy and the safety of full-dose T-DXd during long-course treatment.