S-1 for 9 Months Versus 1 Year for Stage II Gastric Cancer (SMAC）

Inclusion Criteria: 1. The lower age limit of research subjects 18 years old and upper age limit of 75 years old. 2. Be proven to be primary adenocarcinoma of gastric cancer and staged II by pathological evidence 3. R0 surgery with lymphadenectomy 4. Without any other malignancies 5. ECOG (ECOG score standard) performance status of 0 or 1 and expected to survive more than 6 months 6. No contraindications to chemotherapy, including normal peripheral blood routine, liver, and kidney function and electrocardiogram （WBC≥4.0 x 109 /L, NEU≥1.5 x 109 /L, PLT≥100 x 109 /L and HGB≥90g/L). Exclusion Criteria: 1. Female in pregnancy or lactation, or refuse to receive Contraception measures during chemotherapy. 2. Patients with stage I, III and IV. 3. Unavailable for R0 resection and D2 lymph node dissection. 4. Suffering from other uncontrolled diseases, such as other tumors, acute and Chronic infection. 5. With severe heart disease, including congestive heart failure, uncontrolled arrhythmias, unstable angina, myocardial infarction, severe heart valve disease, and resistant hypertension. 6. Any Known or suspected history of drug allergy test. 7. The researchers believe the patient is not able to complete the entire course of the experiment. 8. Patients (within 4 weeks) are receiving any other anti-cancer drugs therapy, biological therapy, radiation therapy, or Immunosuppressive therapy. 9. Patients conform to any of the following: post-organ transplant, necessary for long-term immunosuppressive or suffering with autoimmune diseases.