Considering synergism between docetaxel (D), capecitabine (X), and oxaliplatin (O) and favourable toxicity profile of oxaliplatin over cisplatin, it is to be expected that combination of docetaxel, capecitabine, and oxaliplatin (DXO) will be more effective than other regimens and feasible in advanced gastric cancer. DXO regimen can be also easily administered on out-patient setting. However, so far, DXO combination has not been tried in advanced gastric cancer. The investigators will determine maximum tolerated dose of DXO regimen in this phase I study.

Inclusion Criteria:

• Histologically confirmed unresectable or metastatic advanced gastric adenocarcinoma
• Completion of adjuvant chemotherapy 6 months before the study, or no previous chemotherapy (But, patients who received docetaxel, capecitabine, or oxaliplatin as adjuvant chemotherapy should be excluded.)
• Age 18 to 70 years old
• Eastern Cooperative Oncology Group performance status 0~2
• Adequate bone marrow function: white blood cell counts >4,000/µL, absolute neutrophil count >2,000/µL, and platelets>100,000/µL
• Adequate renal function: creatinine < 1 x upper normal limit (UNL) or creatinine clearance 60ml/min
• Adequate hepatic function: bilirubin < 1.5 x UNL, aspartate aminotransferase (AST)/alanine aminotransferase (ALT) levels < 2.5 x UNL, and alkaline phosphatase < 5 x UNL (except in case of bone metastasis without any liver disease)
• Given written informed consent prior to study-specific screening procedures, with the understanding that the patient has the right to withdraw from the study at any time, without prejudice

Exclusion Criteria:

• Contraindication to any drug contained in the chemotherapy regimen
• Other tumor type than adenocarcinoma
• Presence or history of central nervous system (CNS) metastasis
• Gastric outlet or bowel obstruction
• Evidence of serious gastrointestinal bleeding
• Peripheral neuropathy > grade 1
• History of significant neurologic or psychiatric disorders
• History of another malignancy within the last five years except cured basal cell carcinoma of skin and cured carcinoma in-situ of uterine cervix
• Pregnant or lactating women, women of childbearing potential not employing adequate contraception. Postmenopausal women must have been amenorrheic for at least 12 months to be considered of non-childbearing potential
• Sexually active males and females (of childbearing potential) unwilling to practice conception during the study
• Clinically significant cardiac disease (e.g. severe non-compensated hypertension, non-compensated heart failure, dilated cardiomyopathy, and coronary heart disease with ST segment depression in electrocardiogram) or myocardial infarction within the last 6 months
• Serious pulmonary conditions/illness (e.g. chronic lung disease with hypoxemia)
• Serious metabolic disease such as severe non-compensated diabetes mellitus
• Serious uncontrolled intercurrent infections, or other serious uncontrolled concomitant disease
• Positive serology for the human immunodeficiency virus (HIV)

6 months after completion of study treatment. If patients received another treatment, further evaluation was not done.