Clinicopathologic Characteristics and Prognostic Factors of GIST: NCI 5-year Experience.

Introduction: Gastrointestinal stromal tumors (GISTs) are considered the most prevelant mesenchymal tumorsin the gastrointestinal system.Aim of work: This study aims to evaluate the prognostic variables and clinicopathological features in GISTpatients treated in the national cancer institute.Patients and methods: Ninety non-metastatic GISTs treated with curative surgery between January 2016 andDecember 2020, were the subject of a retrospective investigation. The Cox regression model and the Kaplan-Meiertechnique were used to evaluate survival analysis.Results: The mean age was 59.4±13.3 years, 48.9% were males. Tumors were gastric (77.8%), jejunal andileal (10%) duodenal (6.7%), and rectal (4.4%). Spindle cell tumors constituted 90%. The median mitotic indexwas 6/50 HPF (1-14), and 49% were > 5. Cases were low-risk (16.7%), intermediate-risk (22.2%), and high-risk(61.1%). Most samples tested positive for CD117 (94.4%) and DOG1 (98.3%). Imatinib was used in 14 patients(15.6%) as neoadjuvant and as adjuvant therapy in 65 (72.2%). The 3-year OS and DFS rates were 92.2%(95% CI: 86.9–99.3) and 70.9% (95% CI: 60.7–82.7), respectively. Rectal tumors showed significantly worseOS (P=0.026). Larger tumor size, non-gastric location, mixed histological subtype, high risk, tumor rupture, andhigher mitotic rate were associated with worse DFS. Tumor location was the only independent factor affecting DFS.Conclusion: GISTs were mostly gastric and intermediate to high risk. Imatinib was more commonly usedas adjuvant therapy. Rectal tumors had significantly worse overall survival. Large tumors, non-gastric, mixedhistological subtype, high risk, tumor rupture, and higher mitotic rate were associated with worse disease-freesurvival.