Postoperative Chemoradiotherapy With S-1 in Gastric Cancer

Inclusion Criteria: * Age \> 18 years * Histologically proven gastric adenocarcinoma which is complete resected * ECOG performance status of 1 or lower * Adequate bone marrow function * absolute neutrophil count \[ANC\] ≥1,500µL, 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 \<2 times UNL * No prior chemotherapy Exclusion Criteria: * Other tumor type than adenocarcinoma * Evidence of distant metastasis * Past or concurrent history of neoplasm except for curatively treated non-melanoma skin cancer or in situ carcinoma of the cervix uteri * Uncontrolled infection * Unstable cardiac disease despite treatment, myocardial infarction within months prior to study entry * History of significant neurologic or psychiatric disorders including dementia or seizures * Other serious underlying medical conditions which could impair the ability of the patient to participate in the study * Symptoms of gastrointestinal obstruction * concomitant drug medication: The following drugs cause drug interaction with S-1.