OBJECTIVETo evaluate the prognostic significance of various clinicopathologic parameters in gastrointestinal stromal tumor (GIST), and to study the frequency of c-kit exon 11 mutations in this tumor.

METHODSOne hundred and fifty-six cases of gastric or small intestinal GIST were retrieved from the archival files of the Department of Pathology, Chinese PLA General Hospital. The clinical features, site of occurrence, tumor diameter, mitotic index, coagulative tumor necrosis, and risk grade were studied and analyzed statistically. Tumor DNA was extracted and c-kit exon 11 was amplified. Upon detection by denaturing high-performance liquid chromatography, the amplified exon 11 was sequenced.

RESULTSFor the 83 cases of gastric GIST studied, the mean age of patients was 55.4 years. Follow-up information was available in 62 cases, with 17 cases having local recurrence or distant metastasis. The 5-year survival rate was 66.5% +/- 17.1%. For the 73 cases of small intestinal GIST studied, the mean age of patients was 50.6 years. Follow-up information was available in 43 cases, with 22 cases having local recurrence or distant metastasis. The 5-year survival rate was 61.8% +/- 18.3%. In general, for gastric GIST, age younger than 50 years (P = 0.046), advanced clinical stage (P = 0.0001), large tumor size (P = 0.0001), high mitotic index (P = 0.0001), presence of coagulative tumor necrosis (P = 0.0001), and high risk grade (P = 0.004) were associated with lower survival rate. COX hazard proportional model revealed that advanced clinical stage (P = 0.001), large tumor size (P = 0.001), high mitotic index (P = 0.002) and high risk grade (P = 0.018) indicated worse prognosi. For small intestinal GIST, advanced clinical stage (P = 0.010) and presence of coagulative tumor necrosis (P = 0.036) were associated with lower survival rate. Advanced clinical stage was an independent prognostic factor. A total of 25 cases harbored c-kit mutations. The frequency of c-kit mutations was 32% and 22.5% for gastric and small intestinal GIST respectively. For gastric GIST, c-kit mutations occurred mainly in patients older than 50 years. In contrast, c-kit mutations in small intestinal GIST occurred in the age group of 40 to 49 years.

CONCLUSIONSFor gastric GIST, advanced clinical stage, tumor diameter, mitotic index and risk grade are the main prognostic indicators. For small intestinal GIST, advanced clinical stage and presence of coagulative tumor necrosis indicate poor prognosis. In general, small intestinal GIST is more frequently associated with metastasis and tumor relapse than gastric GIST. The occurrence of c-kit mutations also correlates with age of patients.