[Chemotherapy Strategy in a Case of MSI-High Patients with Gastric Cancer-Case Report]

A 73-year-old woman was referred to our hospital with a chief complaint of black stools and abdominal distention. She was diagnosed with advanced gastric cancer with pyloric stenosis and multiple lymph node metastasis(cT4aN3M0, cStage Ⅲ)and was administered preoperative chemotherapy after laparoscopy and gastric jejunal bypass surgery. The surgical diagnosis was sT4aN3M0P0CY0. After surgery, 2 courses of DS therapy were administered. However, a new liver metastatic lesion was found, and XELOX therapy was selected as the second-line of treatment. Subsequently, enlarged hepatic hilar lymph nodes were found; microsatellite instability testing confirmed MSI-High cancer. Nivolumab was selected as the third- line therapy. After 15 courses, a new liver metastatic lesion appeared. Although Ram+nab-PTX therapy was chosen as the fourth-line therapy, the patient developed myelosuppression after 3 courses. Two years and 4 months after the initial treatment, the patient was considered to have achieved CR. Because drug-induced liver injury had occurred, the Ram therapy was discontinued. The patient has remained in CR for 1 year without receiving any anticancer drugs. This case suggests that for MSI-high patients with gastric cancer, the consideration of treatment strategy should be based on the molecular biological background.