[A Case of Type 4 Gastric Cancer with Peritoneal Dissemination Successfully Treated with Conversion Surgery after Intensive S-1 plus Oxaliplatin Chemotherapy].

S-1 plus oxaliplatin(SOX)chemotherapy is now widely used for the treatment of unresectable gastric cancer but there are few case reports about conversion surgery following SOX. Hereby, we report a case of type 4 gastric cancer with peritoneal dissemination successfully treated with conversion surgery after intensive SOX chemotherapy. A 69-year-old female was diagnosed of type 4 gastric cancer by upper endoscopy(por1, HER2 negative)and peritoneal disseminations were identified on left diaphragm and mesentery under direct vision. After 11 courses of SOX chemotherapy, CT revealed that primary tumor markedly decreased in size. Therefore, staging laparoscopy was performed and peritoneal disseminated lesions disappeared. Peritoneal cytology also turned negative. Subsequently, total gastrectomy and splenectomy were performed. Histology revealed that tumor was categorized as por2, ypT2N3M0, ypStage ⅢA, and Grade 2 in histological evaluation criteria. SOX was continued as an adjuvant chemotherapy for another 6 months and the patients remain healthy without recurrence. Unresectable gastric cancer with peritoneal dissemination can be successfully treated with conversion surgery following SOX chemotherapy and staging laparoscopy was useful to evaluate peritoneal dissemination. When conversion surgery is indicated for gastric cancer with peritoneal dissemination, downstaging should be confirmed by staging laparoscopy.