Prognostic criteria in patients with gastrointestinal stromal tumors: a single center experience retrospective analysis.

Background: Gastrointestinal stromal tumors (GISTs) are morphologically and clinically heterogeneous tumors, and their biological behavior is difficult to predict, ranging from clinically benign to malignant. The aim of our study was to reanalyze the value of the commonly used prognostic criteria and recently reported nomogram in predicting disease recurrence in patients with primary resectable GISTs.

Methods: The clinicopathological features of 60 patients with GISTs who underwent surgical resection between 1998 and 2010 at Hiroshima University Hospital were retrospectively reviewed. Tumors were classified according to the National Institutes of Health and Armed Forces Institute of Pathology criteria, and nomogram predictions were performed. The relationship between patient and tumor characteristics was tested by univariate analysis using the log-rank test. Furthermore, we assessed nomogram performance with the concordance index and calibration.

Results: The median patient follow-up was 4.1 years, with 6 of 60 patients experiencing recurrence. Recurrence was observed only in the high-risk group. The recurrence-free survival (RFS) was 93.0 and 89.9% after 2 and 5 years, respectively. The concordance indices of the nomogram prediction were 0.96 and 0.65 for all patients and the high-risk subgroup, respectively. Calibration of the nomogram-predicted RFS tended to overestimate the recurrence risk relative to the actual RFS.

Conclusions: Although the commonly used criteria provide an excellent estimation of tumor behavior, they are limited by prognostic heterogeneity. The predictive nomogram is a beneficial scoring system but not a direct RFS predictor. We need more consideration for small GISTs, particularly those less than 3 cm in diameter, and small GISTs should be analyzed as a subset with potentiality different biological behavior.