The Relationship Between Microsatellite Instability and Efficacy of Fluorouracil Based Adjuvant Chemotherapy in Gastric Cancer After Operation

Inclusion Criteria: 1. Histopathology or cytopathology proven gastric cancer; 2. Operable advanced gastric cancer patients: primary lesions can be completely excision, no distant metastasis; 3. Postoperative patients who can tolerate 5-FU based (5-FU，S-1 or Capecitabine) adjuvant chemotherapy; 4. Life expectancy of at least 6 months; 5. ECOG（Eastern Cooperative Oncology Group ） score 0-1; 6. Age: 18\~80 years old; 7. Normal hemodynamic indices before the recruitment (including blood cell count and liver/kidney function). * For example: WBC（White blood cell count ）\>4.0×109/L; NEU（Neutrophils）\>1.5×109/L; PLT（Platelet）\>100×109/L; 8. Roughly normal cardiopulmonary function: No coronary heart disease, myocardial infarction, pulmonary heart disease, refractory hypertension; 9. Not concomitant with other uncontrollable benign diseases before the recruitment; 9\. Voluntarily signed the informed consent. Exclusion Criteria: 1. Advanced gastric cancer patients with distant metastasis and inoperable ; 2. Patients who cannot tolerate 5-FU based adjuvant chemotherapy; 3. Pregnant or lactating women; 4. Patients who have no desire to participate in the study.