[A case report of the combination therapy with S-1 plus CDDP intraperitoneal chemotherapy for CY positive cancer patient].

A male patient in his 50s underwent distal gastrectomy for gastric cancer. In operation, there was no peritoneal dissemination. But peritoneal lavage cytology revealed positive peritoneal dissemination. Thus, we set an intraperitoneal infuser port to this patient. On specimen, a type-3 tumor was located in the gastric lesser of antrum to angle. Microscopic examination of specimens revealed a signet ring cell carcinoma and poorly differentiated adenocarcinoma under serosa, and positive of lymph node metastasis. The diagnosis was pT4N2M1P0CY1H0, Stage IV( Japanese classification of gastric carcinoma The 14 Edition). CDDP was administered through the infuser port (on day 7, a first dose of 60 mg/m2 and 30 mg/m2 for second) combined with oral administration of S-1 (100 mg/body) for two weeks, with one week of drug withdrawal. This chemotherapy was repeated for 11 courses. After that, peritoneal lavage cytology became negative. S-1 oral administration was continued for four years, and this patient has been well for five years and six months after the surgery. Therefore, it is suggested that intraperitoneal chemotherapy with cisplatin is an effective treatment for microscopical peritoneal dissemination.