[A case of unresectable Stage IV HER2-positive advanced gastric cancer treated by using trastuzumab combined with chemotherapy].

We observed a case of unresectable Stage IV human epidermal growth factor receptor 2(HER2)-positive advanced gastric cancer treated by using trastuzumab combined with chemotherapy. A 55-year-old man was admitted to our hospital because of dysphagia for 4 months. He was diagnosed with advanced gastric cancer with pyloric stenosis, multiple lung metastases, multiple liver metastases, peritoneal dissemination, and rectal muscle invasion. First, we initiated weekly chemotherapy with paclitaxel. Because the biopsy tissue was HER2-positive, we added trastuzumab to the weekly paclitaxel regimen. After 2 courses, dietary intake became possible, and he was then discharged from our hospital. However, after 3 courses of chemotherapy, disease progression was observed. He was admitted to the hospital again. We inserted a duodenal stent and changed the chemotherapy regimen to fluorouracil plus cisplatin(CDDP)plus trastuzumab. He did not experience any major adverse events during treatment. However, after 2 courses of chemotherapy, he died owing to cancerous peritonitis and intestinal obstruction.