To investigate the predictive values of ¹⁸F-FDG PET/CT image feature and metabolic parameters for the malignant potential of gastrointestinal stromal tumor (GIST).

From March 2014 to June 2020, the ¹⁸F-FDG PET/CT imaging and surgical pathological data of 35 patients with GIST (27 males, 8 females; age 44-84 years) from Union Hospital, Tongji Medical College, Huazhong University of Science and Technology and Zhongnan Hospital of Wuhan University were analyzed retrospectively. Patients were divided into ring-shaped uptake group and other uptake patterns group according to ¹⁸F-FDG PET/CT image feature. Fisher′s exact test was used to analyze the differences of tumor necrosis and National Institutes of Health (NIH) risk classification (short for NIH classification) between different image feature groups. Mann-Whitney U test was used to analyze the differences of SUV_max , metabolic parameters at different thresholds (2.5, 40%, 50%) of SUV_max (metabolic tumor volume (MTV; MTV_2.5, MTV_40%, MTV_50%) and total lesion glycolysis (TLG; TLG_2.5, TLG_40%, TLG_50%)) between different clinicopathological features (lesion location, tumor diameter, mitotic count, Ki-67, necrosis, image feature, NIH classification) groups. Spearman rank correlation analysis was used to explore the correlation between clinicopathological features and metabolic parameters. ROC curve analysis was used to distinguish NIH classification of different metabolic parameters. Delong test was used to compared differences between different AUCs.

Of 35 GIST patients, 11(31.4%) were ring-shaped uptake and 24(68.6%) were other uptake patterns, and the differences of necrosis (7/11 vs 12.5%(3/24); P=0.004) and NIH classification (11/11 vs 25.0%(6/24); P<0.001) between the two groups were significant. There were significant differences of metabolic parameters between different groups of tumor diameter, mitotic count, necrosis, image feature, NIH classification (z values: from -4.70 to -2.09, all P<0.05), while there were no significant differences of Ki-67 (z values: from -0.83 to -0.71, all P>0.05). Metabolic parameters were correlated with mitotic count, tumor diameter, necrosis, image feature and NIH classification (r_s values: 0.36-0.81, all P<0.05), while was not correlated with Ki-67 (r_s values: 0.12-0.14, all P>0.05). The differences of AUCs between SUV_max and MTV_2.5, TLG_2.5, TLG_40%, TLG_50%were significant (0.752, 0.856, 0.856, 0.882, 0.886; z values: 1.96-2.12, all P<0.05).

The NIH classification of GIST with ring-shaped uptake on ¹⁸F-FDG PET/CT is higher and more prone to necrosis. The ¹⁸F-FDG PET/CT metabolic parameters based on different thresholds of SUV_max have certain significance for the prediction of NIH classification of GIST, and may be superior to SUV_max.

Gastrointestinal stromal tumors; Positron-emission tomography; Tomography, X-ray computed; Fluorodeoxyglucose F18; Forecasting