This is a randomized, multicenter, controlled trial to prove efficacy of S-1 and Oxaliplatin as Neoadjuvant Chemotherapy for Advanced Gastric Cancer Patients who undergo D2 gastrectomy.

The primary endpoint is three-year free disease and the second primary includes five-year overall survival, safety and R0 resection rate.

Inclusion Criteria:

1. Histologically confirmed gastric adenocarcinoma

2. Gastroesophageal junction tumour type II or III(NCCN 2009) can be enrolled

3. All patients must undergo EUS,CT(or PET-CT) and laparoscopy to evaluate tumor stage classification (TNM), and only stage II or III (AJCC 7th) gastric cancer patients can be enrolled

4. planning to undergo gastric cancer D2 surgery after neoadjuvant chemotherapy

5. KPS > 60; ECOG performance status 0-2

6. Life expectancy > 6 months

7. Age: 20 to 75 years

8. No other severe disease and life expectancy less than five years

9. 7 days before enrolled, baseline data should be finished including:

   • Granulocyte count ≥ 1.5×109/L;
   • platelet count ≥ 100×109/L;
   • Hemoglobin ≥ 90g/L;
   • hepatic < 1.5×ULN;
   • total bilirubin ≤ 1.0×ULN;
   • creatinine < 1.5×ULN;
   • PT-INR/PTT < 1.7× ULN

10. Disease had to be measurable by the Response Evaluation Criteria in Solid Tumors (RECIST1.1) criteria

11. Written informed consent and able to comply with the protocol

Exclusion Criteria:

1. Patient cannot undergo surgery or chemotherapy because of other severe disease
2. Be allergic to chemotherapy drugs
3. Patients receiving any chemotherapy or drugs involved in this trial in four weeks before enrolled
4. Patients received cytotoxic chemotherapy, targeted therapy, immunotherapy or radiotherapy for gastric cancer
5. Within the last 5 years in patients with a history of other malignant diseases
6. Pregnant or breast-feeding women
7. Severe heart disease like symptoms of coronary heart disease, New York Heart Association (NYHA) grade II or worse congestive heart failure or cardiac arrhythmia having medications or myocardial infarction within the last 12 months
8. Patients with upper gastrointestinal obstruction or absorption anomaly; patient in obstruction of the Helicobacter pylori failure like effect S-1 to take and absorb
9. Patients with a history of peripheral nerve disease
10. Patients who get organ transplant
11. lack of dihydropyrimidine dehydrogenase (DPD)
12. Infection or other disease failure to control