To assess the predictive value of ¹⁸F-FDG PET/CT metabolic parameters in patients with gastrointestinal stromal tumors (GISTs).

The preoperative ¹⁸F-FDG PET/CT imaging and surgical pathological data of 44 patients with GISTs treated at Beijing Cancer Hospital from November 2010 to December 2017 were analyzed retrospectively. Clinicopathological parameters such as sex, age, lesion location, tumor diameter, lymph node metastasis, organ metastasis, mitotic figure, Ki-67 index, CD117 and CD34 expression, NIH risk classification, and WHO prognosis were analyzed by the Chi-square test in patients with positive and negative ¹⁸F-FDG PET/CT imaging results. In patients with positive ¹⁸F-FDG PET/CT imaging results, three PET/CT metabolic indexes (SUVmax, MTV, and TLG) were analyzed by the non-parametric rank sum test in different groups with different clinical or pathological features.

Thirty-one cases had positive ¹⁸F-FDG PET/CT imaging results and 13 cases had negative results. The Chi-square test showed that there were significant differences between the two groups with regard to tumor diameter, mitotic figures, Ki-67 index, NIH risk classification, and WHO prognosis (χ²=13.926, P=0.003; χ²=7.738, P=0.021; χ²=4.233, P=0.040; χ²=24.670, P<0.001; χ²=24.670, P<0.001), but there was no significant difference in sex, age, lesion location, lymph node or organ metastasis, or expression of CD117 and CD34 (P>0.05 for all). Among the 31 ¹⁸F-FDG PET/CT positive cases, MTV and TLG differed significantly between patients with tumor diameter≤5 cm and>5 cm (P=0.003 and 0.004, respectively), but the difference of SUVmax was not significant (P>0.05). SUVmax (P=0.022, 0.023, 0.016, 0.016), MTV (P=0.038, 0.028, 0.004, 0.004), and TLG (P=0.025, 0.014, 0.004, 0.004) differed significantly between patients with different mitotic figures (≤5/50 HPF vs >5/50 HPF), Ki-67 index (≤5% vs >5%), NIH risk classification, or WHO prognosis, while no significant difference was found between patients with different sexes, age (≤60 vs >60 years old), lesion site or density, CD34 expression (presence vs absence), lymph node or organ metastasis (presence vs absence) (P>0.05 for all). Pearson correlation analysis showed that SUVmax (P=0.020, 0.020, 0.014, 0.014), MTV (P=0.037, 0.026, 0.003, 0.003), and TLG (P=0.024, 0.012, 0.003, 0.003) were significantly correlated with pathological features including mitotic figure, Ki-67 index, NIH risk classification, and WHO prognosis. The areas under the ROC curves of the three metabolic parameters (SUVmax, MTV, and TLG) were 0.754, 0.801, and 0.801, respectively.

The metabolic parameters of ¹⁸F-FDG PET/CT have appreciated predictive value in grading the malignant risk of GISTs.