Feasibility study of S-1 for resectable gastric cancer with peritoneal seeding

Despite improvements in chemotherapy and surgical techniques, the prognosis in advanced gastric cancer with peritoneal dissemination still remains very poor. At present, no standard method of treatment has been established for these patients. Therefore, we assessed the feasibility of S-1, a novel oral derivative of 5-fluorouracil, as a postoperative adjuvant chemotherapy for these patients.

Seven patients were enrolled for 1 year. All patients underwent macroscopically curative resection (R1) by an aggressive cytoreductive surgery. S-1 was given orally at a dose of 80 mg/m2/day, for 28 consecutive days followed by a 14-day rest, repeated every 6 weeks.

S-1 was administered for 1 year in 3 out of 7 patients, while the treatment was discontinued in 4 patients due to disease progression. The median S-1 1 cycle given was 5. Grade 2 leukopenia was observed in 3 patients and grade 2 elevation of total bilirubin in one patient. All other adverse reactions were grade 1. The median overall survival was > 696 days with a 1-year survival rate of 85.7%. The median overall progression-free survival was 213 days.

S-1 is feasible as a postoperative adjuvant chemotherapy for resectable gastric cancer with peritoneal seeding.