18F-FDG PET/CT imaging features of hepatic metastases in gastrointestinal stromal tumors / 中华核医学与分子影像杂志

ABSTRACT

Objective:To analyze the imaging features of hepatic metastases in gastrointestinal stromal tumors (GIST) on 18F-fluorodexyglucose (FDG) PET/CT in order to improve the accuracy of diagnosis. Methods:Clinical and imaging data of 33 patients (18 males, 15 females, age 34-70 years) with hepatic metastases in GIST who underwent PET/CT examination between May 2013 and July 2019 in Fujian Cancer Hospital were analyzed retrospectively. All patients underwent 18F-FDG PET/CT early imaging, and nine of them underwent delayed imaging. Visual analysis was performed on the PET/CT images by comparing FDG uptake of hepatic lesions and liver background, and all lesions were classified as significant hypermetabolism, slightly higher metabolism and equal or lower metabolism. Maximum standardized uptake value (SUV max) of primary GIST lesions and hepatic metastases were calculated and compared, and the relationship between them was analyzed. Wilcoxon rank sum test and Spearman rank correlation analysis were used to analyze the data. Results:Among 33 GIST patients, 9 patients had solitary hepatic metastasis, and 24 patients had multiple hepatic metastases (104 lesions). The diameter of metastases was 0.8-14.6(2.2(1.5, 3.9)) cm, and SUV max was 1.4-21.5(3.6(2.4, 5.7)). Of the 104 hepatic metastases, 94.2%(98/104) lesions had clear boundaries, 65.4%(68/104) lesions had uniform density (2 lesions with cystic density), 34.6%(36/104) lesions had uneven density in which hemorrhage, cystic change or necrosis could be found. On visual analysis of PET images, 38.5%(40/104) lesions were with significant hypermetabolism, 26.0%(27/104) were with slightly higher metabolism and 35.6%(37/104) were with equal or lower metabolism. In 24 patients with multiple hepatic metastases, 79.2%(19/24) showed different metabolic levels synchronously. Among 67 hypermetabolic metastases, 34.3%(23/67) were with homogeneous metabolism, of which 13 lesions with diameter<2.0 cm; 65.7%(44/67) were with heterogeneous metabolism, of which 36 lesions with diameter≥2.0 cm. There was a moderate correlation of SUV max between GIST primary tumors and hepatic metastases ( n=15; 9.2(6.8, 14.5) vs 3.8(2.1, 6.0), rs=0.556, P<0.01). The difference of SUV max between GIST primary tumors and hepatic metastases was statistically significant ( z=-5.098, P<0.01). In delayed imaging, 13/15 hepatic metastases with equal or lower metabolism changed to slightly higher metabolism. Conclusions:Hepatic metastases in GIST on 18F-FDG PET/CT imaging usually have clear boundary, and often associate with cystic degeneration, hemorrhage or necrosis. The metabolic patterns of hepatic metastases in GIST are varied. Delayed PET/CT imaging is helpful for the diagnosis of hypometabolic hepatic metastases in GIST.