S-1 and Irinotecan Combination Chemotherapy for Advanced Gastric Cancer

Inclusion Criteria:

* Pathologically proven unresectable adenocarcinoma of stomach
* With uni-dimensionally measurable disease (at least longest diameter 2 cm on conventional CT scan, x-ray or physical examination, or 1cm on spiral CT scan)
* Age 18 to 70 years old
* Estimated life expectancy of more than 3 months
* ECOG performance status of 2 or lower
* Adequate bone marrow function(absolute neutrophil count \[ANC\] ≥1,500/µL, hemoglobin ≥9.0 g/dL,and platelets ≥100,000/µL)
* Adequate kidney function (serum creatinine \< 1.5 mg/dL)
* Adequate liver function (serum total bilirubin \< 2 times the upper normal limit (UNL); serum transaminases levels \<3 times \[\<5 times for patients with liver metastasis\] UNL)
* No prior chemotherapy but prior adjuvant chemotherapy finished at least 6 months before enrollment was allowed. (but, prior adjuvant chemotherapy with capecitabine or S-1 or camptothecin analogues was excluded)
* No prior radiation therapy for at least 4 weeks before enrollment in the study

Exclusion Criteria:

* Other tumor type than adenocarcinoma
* Central nervous system (CNS) metastases or prior radiation for CNS metastases
* Gastric outlet obstruction or intestinal obstruction
* Evidence of gastrointestinal bleeding
* The patient has bony lesions as the sole evaluable disease.
* Past or concurrent history of neoplasm other than stomach cancer, except for curatively treated non-melanoma skin cancer or in situ carcinoma of the cervix uteri
* Pregnant or lactating women, women of childbearing potential not employing adequate contraception
* Other serious illness or medical conditions

  * Unstable cardiac disease despite treatment, myocardial infarction within 6 months prior to study entry
  * History of significant neurologic or psychiatric disorders including dementia or seizures
  * Active uncontrolled infection
  * Other serious underlying medical conditions which could impair the ability of the patient to participate in the study
* Concomitant administration of any other experimental drug under investigation, or concomitant chemotherapy, hormonal therapy, or immunotherapy
* concomitant drug medication; The following drugs cause drug interaction with S-1.

  i. Warfarin, phenprocoumon: increase bleeding tendency ii. Increase blood concentration of phenytoin iii. sorivudine: inhibit DPD -\> increase toxicity according to fluoropyrimidine iv. allopurinol : decrease activity of S-1