Factors Affecting Disease-Free Survival in Operated Nonmetastatic Gastrointestinal Stromal Tumors

Background: Possibly originating from interstitial Cajal cells, gastrointestinal stromal tumors (GISTS) have variable biological behaviors. In this study, we aimed to examine the factors affecting the disease-free survival (DFS) in patients with GIST who underwent operation. Material and methods: The study included the patients who were followed up and treated for GIST in our oncology clinic between 2002 and 2017. The Armed Forces Institute of Pathology criteria (Miettinen risk score) were used for risk stratification of patients. Results: Seventy-four patients were included to the study, where female patients constituted 52.7%, and the median age was 56 (range: 24-83) y. Most common primary tumor location was the stomach (51.4%), followed by the small intestine (33.8%), colorectum (10.8%), and retroperitoneum (4.1%). Miettinen risk score showed 12 patients (16.7%) at very low risk, 15 patients (20.8%) at low risk, 18 patients (25%) at intermediate risk, and 27 patients (37.5%) at high risk. DFS was significantly lower in patients with small intestine involvement than in cases with stomach involvement (P = 0.004). DFS was significantly lower in patients at high risk than in patients with no high risk (P = 0.034). Small intestine localization (hazard ratio [HR], 8.98; 95% confidence interval [CI], 1.14-8.18), high-risk score (HR, 5.16; 95% CI, 1.42-12.75), c-kit positivity (HR, 0.24; 95% CI, 0.13-0.69), and adjuvant therapy (HR, 0.37; 95% CI, 0.20-0.92) were found to be the most significant factors affecting DFS. Conclusions: Our study showed negative effects of small intestine localization and high-risk category and positive effects of c-kit positivity and adjuvant therapy on DFS in patients with GIST who underwent operation. When a decision will be made in favor of adjuvant therapy, tumor localization and c-kit mutation should also be considered in addition to risk score. (C) 2019 Elsevier Inc. All rights reserved.