RATIONALE: Drugs used in chemotherapy, such as S-1 and irinotecan, work in different ways to stop the growth of tumor cells, either by killing the cells or by stopping them from dividing. Giving more than one drug (combination chemotherapy) may kill more tumor cells. Giving chemotherapy before surgery may shrink the tumor so that it can be completely removed.

PURPOSE: This phase II trial is studying how well giving S-1 together with irinotecan works in treating patients who are undergoing surgery for locally advanced stomach cancer.

OBJECTIVES:

Primary

• Determine the efficacy of neoadjuvant S-1 and irinotecan in patients with locally advanced gastric cancer.

Secondary

• Determine the histological response in patients treated with this regimen.
• Determine the overall survival of patients treated with this regimen.
• Determine the progression-free survival of patients treated with this regimen.
• Determine the toxicity of this regimen in these patients.
• Determine postoperative morbidity in patients treated with this regimen.
• Determine the rate of potentially curative surgery in patients treated with this regimen.

OUTLINE: This is a multicenter study.

Patients receive oral S-1 on days 1-21 and irinotecan IV over 90 minutes on days 1 and 15. Treatment repeats every 28 days for 2 courses in the absence of disease progression or unacceptable toxicity. Patients then undergo gastrectomy with lymphadenectomy. After surgery, patients resume treatment with S-1 alone as before for 1 year.

PROJECTED ACCRUAL: A total of 70 patients will be accrued for this study.

DISEASE CHARACTERISTICS:

• Histologically confirmed gastric adenocarcinoma

  • Locally advanced disease

    • Clinical stage T3-4, N0-3, M0 (according to the Japanese gastric cancer classification)

• Planning to undergo curative surgery after neoadjuvant chemotherapy

PATIENT CHARACTERISTICS:

Age

• 20 to 75

Performance status

• ECOG 0-1

Life expectancy

• Not specified

Hematopoietic

• WBC 4,000-12,000/mm^3
• Granulocyte count ≥ 2,000/mm^3
• Platelet count ≥ 100,000/mm^3
• Hemoglobin ≥ 9.0 g/dL

Hepatic

• AST and ALT ≤ 100 U/L
• Bilirubin ≤ 1.5 mg/dL

Renal

• Creatinine normal OR
• Creatinine clearance ≥ 50 mL/min

Pulmonary

• PaO_2 > 60 mm Hg on room air

Other

• Able to swallow oral medication

PRIOR CONCURRENT THERAPY:

Biologic therapy

• No prior biologic therapy for gastric cancer

Chemotherapy

• No prior chemotherapy for gastric cancer

Endocrine therapy

• No prior endocrine therapy for gastric cancer

Radiotherapy

• No prior radiotherapy for gastric cancer

Surgery

• No prior surgery for gastric cancer

Other

• No other prior therapy for gastric cancer