[A Case of HER2 Positive Unresectable Gastric Cancer Leading to Conversion Therapy with Chemotherapy].

A 72‒year‒old man visited our hospital with a chief complaint of epigastralgia. Upper gastrointestinal endoscopy revealed type 3 advanced gastric cancer at the body of the stomach. Following an investigation, he was diagnosed with human epidermal growth factor receptor 2‒positive gastric cancer with invasion to the pancreas as well as the paraaortic lymph node, and multiple liver metastases were also observed. The cancer was judged to be cT4a, N2M1(H1 LYM: No. 16), cStage Ⅳ and thus was considered suitable for chemotherapy. We performed capecitabine plus cisplatin plus trastuzumab therapy. After 3 courses, the primary lesion and swollen lymph nodes decreased in size. After 20 chemotherapy courses, the primary lesion relapsed, so conversion surgery was performed. The patient underwent total gastrectomy, distal pancreatectomy, and partial resection of the liver. We planned to perform adjuvant chemotherapy, but the patient declined it because of anorexia. At 18 months after the operation, recurrence of the tumor was detected at the celiac artery. Chemotherapy was performed as follows: capecitabine plus trastuzumab 10 courses, ramucirumab plus paclitaxel, irinotecan, and nivolumab. However, the patient eventually died 71 months after the first visit.