[A case of advanced gastric cancer with multiple liver, lung, and lymph node metastases treated with S-1, CDDP, and trastuzumab].

Abstract The patient was a 58-year-old man diagnosed with type 2 advanced gastric cancer located at the fundus with multiple liver, lung, and lymph node metastases(Stage IV). Examination of an endoscopically obtained biopsy specimen revealed poorly differentiated adenocarcinoma (por), which stained positive for human epidermal growth factor receptor 2 (HER2) on immunohistochemistry. We started chemotherapy with S-1 plus cisplatin (CDDP) plus trastuzumab. The treatment was effective, as the tumor had reduced in size by 22.5% and 36.2%(partial response[PR])after 3 and 6 courses, respectively. Adverse events related to the treatment were limited to grade 1 fever, nausea, vomiting, and diarrhea. The patient's chief complaints of right upper abdominal pain and abdominal fullness remarkably improved after treatment initiation. Although the therapy was effective against the multiple liver metastases and could be continued for 11 courses, the lymph nodes metastases did not respond to therapy (progressive disease [PD]), and the patient died 9 months after the start of treatment. Chemotherapy with S-1 pus CDDP plus trastuzumab may be effective for HER2-positive advanced gastric cancer with liver metastasis.