OBJECTIVES: Primary * Determine the efficacy and feasibility of neoadjuvant chemotherapy comprising S-1 and cisplatin in patients with stage IV gastric adenocarcinoma. * Determine the overall survival of patients treated with this regimen. Secondary * Determine the time to progression and types of initial recurrence in patients treated with this regimen. * Determine tumor response in patients treated with this regimen. * Determine mortality and morbidity related to treatment in these patients. * Determine the toxicity of this regimen in these patients. OUTLINE: This is a multicenter study. Patients receive oral S-1 on days 1-21 and cisplatin IV over 2 hours on day 8. Treatment repeats every 35 days for 2 courses in the absence of disease progression or unacceptable toxicity. Patients then undergo gastrectomy with lymphadenectomy. Patients resume oral S-1 after surgery. PROJECTED ACCRUAL: A total of 50 patients will be accrued for this study.
DISEASE CHARACTERISTICS: * Histologically confirmed gastric adenocarcinoma * Stage IV disease meeting 1 of the following staging criteria according to Japanese gastric cancer classification: * T4, N2 * T4, N3 * P1, CY1 * CT scan and laparoscopic staging required PATIENT CHARACTERISTICS: Age * 20 and over Performance status * ECOG 0-1 Life expectancy * Not specified Hematopoietic * WBC ≥ 4,000/mm\^3 AND \< 12,000/mm\^3 * Granulocyte count ≥ 2,000/mm\^3 * Platelet count ≥ 100,000/mm\^3 * Hemoglobin ≥ 9.0 g/dL Hepatic * AST and ALT ≤ 2.5 times upper limit of normal * Bilirubin ≤ 1.5 mg/dL Renal * Creatinine clearance ≥ 50 mL/min Pulmonary * PaO_2 ≥ 70 mm Hg on room air Other * Able to swallow oral medication PRIOR CONCURRENT THERAPY: Biologic therapy * Not specified Chemotherapy * No prior chemotherapy for gastric cancer Endocrine therapy * Not specified Radiotherapy * No prior radiotherapy for gastric cancer Surgery * No prior surgery for gastric cancer Other * No other prior therapy for gastric cancer