Prospective Multicenter Clinical Study of Neoadjuvant Imatinib Mesylate for Gastrointestinal Stromal Tumors

Inclusion Criteria: * Preoperative histologically confirmed primary gastrointestinal stromal tumor * Tumor must stain positive for c-Kit (CD117) and/or discovered on gist-1 (DOG-1) by immunohistochemistry * Gene mutation test report including c-kit exons 9,11,13 and 17 and platelet-derived growth factor receptor alpha (PDGFRA) exons 12 and 18 * High risk GIST (as modified National Institutes of Health (NIH) 2008): stomach (maximum tumor diameter\> 10.0cm), nonstomach (maximum tumor diameter\> 5.0cm) * Gender is not limited. Age: ≥ 18 years and ≤ 80 years old * Performance status: Eastern Cooperative Oncology Group (ECOG) 0-1 * Patient had informed consent and signed a written consent form Exclusion Criteria: * Asp842Val (D842V) mutation in Exon 18 of PDGFRA gene, or wild type (c-kit exon 9,11,13,17, and PDGFRA Exon 12,18), or c-kit exon 9 mutation * Treated with tyrosine kinase inhibitors including Imatinib * Aspartate aminotransferase (AST) and/or Alanine aminotransferase (ALT)\>2.5×ULN(upper limit of normal)，or Total bilirubin (TBIL)\>1.5×ULN，or Creatinine (Cr)\>1.0×ULN * Absolute neutrophil count (ANC) \< 1.5 × 10 \^ 9 / L；or Platelet count (PLT) \< 75 × 10 \^ 9 / L；or Hemoglobin (Hb) ≥ 90 g / L * Previous or concurrent other active malignant tumors (except for basal cell carcinoma of the skin, or cervical cancer in situ that has undergone curative therapy) * Distant metastases are present * Any of the following conditions during the 12 months prior to entry: myocardial infarction, severe / unstable angina, coronary artery / peripheral artery bypass surgery, symptomatic congestive heart failure, or cerebrovascular accidents * positive Human Immunodeficiency Virus (HIV) antibody * Currently participating in other clinical trials * Pregnant or lactating women or have fertility without taking contraception * Suffering from other serious acute and chronic physical or mental problems, or abnormal laboratory tests, will increase the risk of participation or drug use, or interfere with the judgment of the findings, judged by the researchers as participate in the study