To assess the usefulness of irinotecan plus S-1 therapy based on the antitumor effect and survival period. by performing a phase II study of this combination in patients with inoperable or with postoperative gastric cancer

A multicenter Open-label, single-arm, phase II clinical trial is conducted on patients with histological stage IV gastric cancer given irinotecan plus S-1. The usefulness of this regimens as 1st line therapy for gastric cancer was evaluated by the disease-free survival rate (DFR), overall survival rate (OS), incidence and severity of adverse event.

Inclusion Criteria:

・ Eligibility criteria

1. Histological diagnosis of gastric adenocarcinoma.
2. Measurable or assessable lesions.
3. Age: 18 ~ 75 years.
4. Performance Status (ECOG): 0 ~ 2.
5. No prior chemotherapy or only one regimen of previous chemotherapy (with a washout period >4 weeks after the final day of the previous therapy). Adjuvant chemotherapy is not defined as previous therapy.
6. No history of treatment with CPT-11 or S-1.
7. No history of radiotherapy to the abdomen.
8. Oral intake of S-1 is possible.
9. Adequate function of major organs (bone marrow, heart, lungs, liver etc.). WBC 3,500/mm3 and 12,000/mm3. Hb 10.0 g/dl. Platelet count 100,000/mm3. GOT and GPT 2.5times the upper limit of normal (excluding liver metastasis). T-Bil 2.0mg/dl. Creatinine <1.5 mg/dl (but if it is 1.0 ~ 1.5 mg/dl, the dose of S-1 can be decreased according to the dose reduction criteria to allow registration in the trial). Normal ECG (not considering clinically unimportant arrhythmias and ischemic changes). (10) Predicted survival for >3 months.

(11) Able to give written informed consent

Exclusion Criteria:

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