The aim of this phase II trial was to evaluate the feasibility, efficacy and tolerability of intensity-modulated radiotherapy combined with S-1 based chemotherapy in patients with pathologically positive lymph node after completely resected gastric cancer. Furthermore, the investigators sought to compare the dosimetric differences between the volumetric-modulated arc therapy (VMAT), Tomotherapy and intensity-modulated radiotherapy (IMRT) techniques in treatment planning for gastric cancer as adjuvant radiotherapy.

Inclusion Criteria:

• Pathologically proven positive lymph node gastric adenocarcinoma in patients undergoing R0 resection

• Any prior chemotherapy is allowed in this protocol

• No distant metastasis in liver,lung,,bone,central nervous system(CNS),no peritoneal transplantation

• No prior abdominal or pelvic radiotherapy

• Karnofsky performance status(KPS)≥ 70, predictive life span no less than 6 months

• Patients must have normal organ and marrow function as defined below:

  • Leukocytes greater than or equal to 3,000 G/L
  • Platelets: greater than or equal to 100,000/mm3
  • Hemoglobin:greater than or equal to 10g/L
  • Total bilirubin: within normal institutional limits
  • AST/ALT: less than or equal to 1.5 times the upper limit
  • Creatinine within normal upper limits

• Informed consent

Exclusion Criteria:

• Patients with other cancer history except cervical carcinoma in situ and non-malignant melanoma skin cancer
• With any distant metastasis in liver,lung,,bone,CNS,or peritoneal transplantation
• History of allergic reactions attributed to similar chemical or biologic complex to S-1
• Uncontrolled illness including, but not limited to, active infection, symptomatic heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness
• History of myocardial infarction within the past 6 months or history of ventricular arrhythmia
• History of prior radiation to the abdomen
• Pregnant or lactating females