Methods
The clinicopathological and follow-up data of 497 operable GIST patients admitted to Department of General Surgery, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University between 1997 and 2012 were reviewed. Each diagnosis of "GIST" was confirmed by postoperative histopathology and immunohistochemistry assay (IHCA). The results of histopathological features and IHCA findings of every case were reviewed by 2 experienced pathologists. Those diagnosed as "gastrointestinal stromal mesenchymal tumor" prior to 2000 were re-examined by IHCA to confirm the diagnosis of GIST. The tumors were categorized into very low, low, intermediate and high risk groups according to the modified NIH risk classification criteria (Table 1). Only the cases with complete medical records and pathological data were involved in present study. The following parameters were reviewed and analyzed: age, sex, clinical presentation, surgical detail, tumor site, tumor size, mitotic rate, IHCA (CD117, CD34, vimentin, smooth muscle actin (SMA), S-100, Discovered On GIST 1 (DOG1)), TKI therapy and outcome. Survival outcome in terms of overall survival (OS), relapse-free survival (RFS), and progression-free survival (PFS) were assessed. OS was defined as the period from surgery to the last follow-up or death. RFS was defined as the period from surgery to the time of clinical or radiological evidence of disease relapse. PFS in patients who had metastatic or recurrent disease was defined as the period from the time when relapse was diagnosed to clinical or radiological evidence of progression or death.
All patients provided written informed consent for their information to be stored in the hospital database, and we obtained separate consent for use of research. Study approval was obtained from independent ethics committees from Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University. The study was undertaken in accordance with the ethical standards of the World Medical Association Declaration of Helsinki.
χ test and Fisher's exact test were performed to analyze qualitative parameters and Kaplan-Meier method with log rank test was used for postoperative survival analysis. Independent factors were identified in multivariate analysis by COX proportional hazard analysis with forward selection at P < 0.05. Odds ratios (ORs) and 95% confidence intervals (CIs) were determined using unconditional multiple logistic regression models. Two-sided P values of 0.05 or less were considered to indicate statistical significance.