Docetaxel Versus Docetaxel Plus Cisplatin Versus Docetaxel Plus S-1 as Second-line Chemotherapy in Metastatic Gastric Cancer

Inclusion Criteria:

* Histologically or cytologically confirmed gastric adenocarcinoma with metastatic disease
* Age ≥18 years
* Eastern Cooperative Oncology Group performance status 0-2
* At least one measurable lesion as defined by RECIST
* Only one prior chemotherapy containing both S-1 or capecitabine and cisplatin for metastatic gastric cancer with documented progression of disease occurring during chemotherapy or within 6 months of completion of chemotherapy
* Adequate major organ function:

ANC ≥1,500/mm3, Platelet ≥100,000/mm3, serum bilirubin ≤1.5 x upper limit of normal (ULN), AST/ALT ≤2.5 x ULN (≤5 x ULN if liver metastases are present), creatinine clearance ≥50 ml/min using the calculation formula or 24 hours urine collection

* Patients should sign a written informed consent before study entry

Exclusion Criteria:

* Prior taxane treatment
* Major surgery or radiotherapy less than 4 weeks prior to entry
* NCI CTCAE (version 3.0) adverse events ≥grade 2 except alopecia, fatigue, and weight loss
* Lack of physical integrity of the upper gastrointestinal tract or malabsorption syndrome, or inability to take oral medication
* Patients with active gastrointestinal bleeding
* Inadequate cardiovascular function
* Serious concurrent infection or nonmalignant illness that is uncontrolled or whose control may be jeopardized by complications of study therapy
* Other malignancy within the past 3 years except adequately treated non-melanomatous skin cancer, carcinoma in situ of the cervix, or in situ of prostate cancer Gleason≤7
* Psychiatric disorder that would preclude compliance
* Patients receiving a concomitant treatment with drugs interacting with S-1 such as flucytosine, phenytoin, or allopurinol
* Female patients who are pregnant or breast feeding or adults of reproductive potential not employing effective method of birth control