Adjuvant Capecitabine Versus Observation Alone in Curatively Resected Stage IB Gastric Cancer((KCSG ST14-05): CATALYSIS

Inclusion Criteria:

* Curatively resected gastric or gastroesophageal junction adenocarcinoma
* Pathologic stage IB (by AJCC 6th edition) with at least one additional risk factor for recurrence (additional risk factors for recurrence include age \>65 years, male gender, presence of lymphovascular invasion, presence of perineural invasion).
* Age: 18 -74years
* ECOG performance status: 0-2
* Adequate bone marrow function (ANC \>1,500/uL, Platelets 100,000/uL, and Hb \> 8.0 g/dL)
* Adequate renal function (serum creatinine \< 1.5 mg/dL)
* Adequate hepatic function (bilirubin \< 1.5 mg/dL, ALT and AST \< 3 times upper limit of normal)
* Written informed consent

Exclusion Criteria:

* Pregnant or lactating women.
* Women of childbearing potential with either a positive pregnancy test at baseline. Postmenopausal women must have been amenorrheic for at least 12 months to be considered of non-child bearing potential.
* Sexually active males and females (of childbearing potential) unwilling to practice contraception during the study medication and until 3 months after discontinuation of the study medication.
* Any evidence of metastatic disease (including presence of tumor cells in the ascites).
* Previous chemotherapy or radiotherapy for the currently treated gastric cancer.
* No recovery from serious complications of gastrectomy.
* History of another malignancy within the last five years except cured basal cell carcinoma of skin and cured carcinoma in-situ of uterine cervix.
* History of uncontrolled seizures, central nervous system disorders or psychiatric disability judged by the investigator to be clinically significant precluding informed consent or interfering with compliance for oral drug intake.
* Clinically significant (i.e. active) cardiac disease: e.g. unstable angina, symptomatic coronary artery disease, New York Heart Association (NYHA) grade II or greater congestive heart failure or serious cardiac arrhythmia requiring medication or myocardial infarction within the last 6 months.
* Lack of physical integrity of the upper gastrointestinal tract or those who have malabsorption syndrome likely to influence absorption of capecitabine, or inability to take oral medication.
* Serious uncontrolled intercurrent infections or other serious uncontrolled concomitant disease.
* Organ allografts requiring immunosuppressive therapy.
* Received any investigational drug or agent/procedure, i.e. participation in another trial within 4 weeks before randomization.
* Requirement for concurrent use of the antiviral agent sorivudine (antiviral) or chemically related analogues, such as brivudine.
* Positive serologic test for HIV