Multiparametric MRI and 18F-FDG PET features for differentiating gastrointestinal stromal tumors from benign gastric subepithelial lesions.

OBJECTIVES

To investigate whether multiparametric magnetic resonance imaging (MRI) and 18F-fluorodeoxyglucose positron emission tomography (PET) can be helpful in differentiating gastrointestinal stromal tumors (GISTs) from non-GISTs and high-risk GISTs from low-risk GISTs.

METHODS

This retrospective study included 56 patients with pathologically confirmed GISTs (n = 39), leiomyoma (n = 8), schwannoma (n = 5), heterotopic pancreas (n = 3), and glomus tumor (n = 1) who underwent MRI and/or PET examinations. Two radiologists reviewed MRI regarding location, shape, contour, growth pattern, margin, signal intensity (SI) on T1- (T1WI) and T2-weighted images (T2WI), degree and pattern of enhancement, hemorrhage, and necrosis. Mean apparent diffusion coefficient (ADC) and maximum standardized uptake value (SUVmax) were measured. Imaging features were compared among non-GISTs, low-risk GISTs, and high-risk GISTs using uni- and multivariate statistical analyses.

RESULTS

Size, longitudinal location, shape, contour, growth pattern, SI on T1- and T2WI, enhancement pattern, hemorrhage, necrosis, ADC, and SUVmax were significantly different among non-GISTs, low-risk GISTs, and high-risk GISTs (p < 0.05). On multivariate analysis, SI on T2WI (hazard ratio [HR], 66.0; p = 0.002) was the only independent variable for differentiating GISTs from non-GISTs whereas enhancement pattern (HR, 56.0; p = 0.041), ADC (HR, 0.997; p = 0.01), and SUVmax (HR, 2.08; p = 0.027) were significant features for differentiating between high-risk and low-risk GISTs.

CONCLUSIONS

Several qualitative and quantitative MRI and PET features including ADC and SUVmax values are significantly different among non-GISTs, low-risk GISTs, and high-risk GISTs. Multiparametric information obtained from MRI with or without PET can be useful for differentiation of gastric subepithelial tumors as well as for determining patients' management and prognosis.

KEY POINTS: • Several qualitative MRI features are helpful in distinguishing gastrointestinal stromal tumors (GISTs) from non-GISTs as well as high-risk GISTs from low-risk GISTs. • Apparent diffusion coefficient value on diffusion-weighted imaging can be useful in distinguishing GISTs from non-GISTs as well as high-risk GISTs from low-risk GISTs. • PET has the potential to distinguish between high-risk and low-risk GISTs.