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Characterization of malignant gastrointestinal stromal tumors-a single center experience.

Background
The recurrence rate, related to the unpredictable behavior of gastrointestinal stromal tumors (GISTs), continues to be a major topic of investigation, since no actual risk evaluation scales have proven to be exceedingly effective in predicting prognosis. We therefore focus in this study on investigating the predictive variables of disease recurrence.


Methods
Between September 2004 and January 2011, 34 patients, 18 males and 16 females with a median age of 62 (range, 27-87) years, underwent operations for primary, localized and advanced GISTs. Immunohistochemical profile, KIT and the platelet-derived growth factor receptor-alpha (PDGFR-α) gene mutations, tumor size, tumor site, mitotic index, synchronous tumors, adjuvant therapy, symptoms and gender were considered and analyzed as predictive variables. The receiver operating characteristic (ROC) analysis was used to determine the optimal cut-off value for tumor dimension to predict recurrence.


Results
The median follow-up (FU) was 20 months (range, 6-86 months). A first-line adjuvant therapy was performed in nine patients. Disease relapse occurred in five cases. The tumor size and the mitotic index were the strongest predictive factors (P<0.001). The optimal maximum value for the tumor size was 7 cm [area under the curve (AUC) =0.955].


Conclusions
In light of the most recent evidence, a tumor size of 7 cm should be considered the threshold value for malignancy, and smaller GISTs with low mitotic counts as tumors with a low-grade risk.