Study of Oxaliplatin, Irinotecan, and S-1 in Gastric Cancer

Inclusion Criteria: * Pathologically confirmed advanced, recurrent or metastatic adenocarcinoma of stomach (stage IV by primary tumor, regional nodes, metastasis(TNM) staging system) * Eastern Cooperative Oncology Group (ECOG) performance status 0-2 * More than 3 months expected life span * Measurable lesion by RECIST criteria version 1.1 * Palliative chemotherapy naive * Adequate organ functions * Participants must sign an informed consent indicating that they are aware of the investigational nature of the study in keeping with the policy of the hospital Exclusion Criteria: * Positive Her2 status on participants' cancer tissue. * Any prior 2 years or concurrent malignancy other than non-melanoma skin cancer, in situ cancer of uterine cervix, or papillary or follicular thyroid cancer. * Participants who had received radiation therapy for target lesions 4 weeks before study enrollment * Participants who had received major surgery 4 weeks before study enrollment * Participants with active infection, severe heart disease, uncontrollable hypertension or diabetes mellitus, myocardial infarction during the preceding 12 months, pregnancy, or breast feeding * Participants with central nervous system(CNS) metastases * Participants with peripheral sensory neuropathies with impaired functional activities * Participants with gastrointestinal obstruction or bleeding inducing mal-absorption of oral chemotherapeutic agents.