Twenty-four-month Progression-free Survival in HER2-amplified Advanced Gastric Cancer with Brain Metastases after Trastuzumab Deruxtecan Treatment: A Case Report and Literature Review

Background: Trastuzumab deruxtecan (T-DXd) has shown promising outcomes as a second or subsequent-line treatment for human epidermal growth factor-2 (HER2)-positive advanced gastric or gastroesophageal junction cancer. Case Presentation: We reported a 49-year-old male patient with stage IV HER2-amplified gastric cancer. Despite extensive pretreatments, including first-line trastuzumab plus FOLFOX, second-- line trastuzumab plus FOLFOX, followed by traditional Chinese medicine, third-line nivolumab plus trastuzumab, fourth-line pyrotinib plus paclitaxel and five hepatic arterial chemoembolization procedures, and fifth-line pembrolizumab plus nab-paclitaxel and thoracic radiotherapy, the patient experienced disease progression. In April 2021, T-DXd was initiated as the sixth-line therapy in combination with radiotherapy for brain metastases. After one treatment cycle, the patient achieved a partial response. T-DXd was discontinued in August 2022 due to recurrent anemia attributed to cardiac stenosis-related bleeding. Conclusion: The condition of the patient remained stable until May 2023, indicating a progression- free survival of over 24 months. This case suggests that T-DXd may offer long-term clinical benefits in patients with HER2-amplified advanced gastric cancer with brain metastases.