Metabolic behavior and prognostic role of pretreatment 18F-FDG PET/CT in gist.

AIM: The metabolic behavior and the prognostic value of 18 F-FDG-PET/CT in gastrointestinal stromal tumor (GIST) is not well investigated. The aim of this study was to analyze the metabolic behavior of GIST and the prognostic role of pretreatment PET/CT features. METHODS: In this retrospective study, we included 35 patients with a diagnosis of GIST who underwent a pretreatment 18 F-FDG-PET/CT scan. We analyzed PET images visually and semiquantitatively by measuring several metabolic parameters as the maximum standardized uptake value corrected for body weight (SUVbw), for lean body mass (SUVlbm), for body surface area (SUVbsa), metabolic tumor volume (MTV) and total lesion glycolysis (TLG). The Kaplan-Meier method was used to measure the progression free survival (PFS) and overall survival curves. RESULTS: Twenty-nine (82%) patients showed a positive 18 F-FDG-PET/CT, whereas the remaining 6 had no hypermetabolic lesions. 18 F-FDG-avidity was significantly related with mitotic index, tumor stage and tumor risk group. Instead, semiquantitative PET/CT parameters correlated only with tumor risk group. Disease progression occurred in 16 patients whereas death in seven. 18 F-FDG-avidity, MTV and TLG were the only variables significantly associated with PFS. CONCLUSION: An 82% rate of PET avidity in GIST was found and it was correlated with stage, tumor risk group and mitotic index. Only baseline 18 F-FDG-avidity, MTV and TLG were independently correlated with PFS.