The optimal regimen for adjuvant treatment has not been established in GC yet. We plan to compare TS-1, TS-1/oxaliplatin with or without RT in D2 resected gastric cancer.

Inclusion Criteria:

1. Histologically proven gastric or gastroesophageal adenocarcinoma
2. ≥ D2 lymph node dissection, curative gastrectomy
3. Stage II, III (AJCC 2010) with any N (any stage with N0 will be excluded)
4. Age > 19
5. ECOG 0-2
6. No distant metastasis
7. Adequate bone marrow functions (ANC ≥ 1,500/ul, blood platelet ≥ 100,000/ul, haemoglobin ≥ 10g/dl, transfusion allowed)
8. Adequate renal functions(serum creatinine ≤ 1.5mg/dl)
9. liver functions (serum bilirubin ≤ 1.5mg/dl, AST/ALT ≤ 3 times(normal value)
10. Written informed consent
11. Possible oral intake (food, drug)

Exclusion Criteria:

• Subjects presenting with any of the following will not be included in the study

  1. Active infection requiring antibiotics
  2. Pregnant, lactating women
  3. Concurrent systemic illness not appropriate for chemotherapy
  4. Resection margin (+) at permanent pathology
  5. Pathologic stage I or IV (Ia or Ib according to AJCC 2010)
  6. Inadequate surgery including D0, D1 resection, dissected LNs less than 12
  7. Paraaortic lymph node (+), pathologically proven
  8. women of potential childbearing not employing adequate contraception