XELOX With Capecitabine Maintenance or XELOX in Elderly Metastatic Adenocarcinoma of Stomach

Inclusion Criteria:

* Ages Eligible for Study: 65 Years or older
* Genders Eligible for Study: Both
* The Eastern Cooperative Oncology Group (ECOG) status ≤ 2
* Histologically confirmed gastric adenocarcinoma(including LAUREN type).
* Measurable disease(according to the Response Evaluation Criteria in Solid Tumors (RECIST) criteria 1.1).
* chemotherapy naive after recurrence or metastasis. Previous neo-adjuvant or adjuvant treatment for gastric cancer, if applicable, more than 6 months.
* Hb \> 90g/L, neutrophil count \> or = 1.5\*10\^9/L, platelet \> or = 100\*10\^9/L, alanine transaminase (ALT) and aspartate aminotransferase (AST) \< or = 2.5 times upper limit of nominal (ULN), alkaline phosphatase (ALP) \< or = 2.5 times ULN, total bilirubin (TBIL) \< 1.5 times ULN, serum albumin level \> or = 30g/L, serum creatinine \< 1 times ULN.
* No serious concomitant diseases which could lead to death within 5 years. At least 5 years from the last Biological/Immunotherapy/Hormone treatment for Malignancy excluding gastric cancer.
* Able to accept oral medication
* Compliance with protocol

Exclusion Criteria:

* Had received cytotoxic chemotherapy, radiotherapy or immunotherapy for this gastric cancer, excluding Corticosteroids.
* Other previous malignancy within 5 year, except curative skin cancer or carcinoma in situ of uterine cervix.
* Uncontrolled epilepsy, central nervous system disorders, or a history of mental disorders.
* clinically significant(i.e. active)cardiac disease e.g. symptomatic coronary artery disease, New York Heart Association (NYHA) II or more serious congestive heart failure or severe requiring medication intervention arrhythmia, or history of myocardial infarction within the last 12 months.
* Upper gastrointestinal obstruction or physiological dysfunction or suffering from malabsorption syndrome, which could affect the absorption of capecitabine.
* Organ transplantation requires immunosuppressive treatment.
* Severe uncontrolled recurrent infections, or Other serious uncontrolled concomitant diseases.
* Moderate or severe renal impairment(creatinine clearance (CCr) = or \< 50 ml/min), or serum creatinine \> ULN.
* Known enzyme deficiency of dihydropyrimidine dehydrogenase(DPD).
* Allergy to Oxaliplatin or any study medication ingredients.