Added value of [ 18 F]FDG PET/MRI over MDCT alone in the staging of recurrent gastric cancer

To investigate whether 2-[18F]fluoro-2-deoxy-D-glucose ([18F]FDG) positron emission tomography/magnetic resonance imaging (PET/MRI) can improve the diagnostic performance of TNM staging and help in making an accurate decision regarding resectability in patients with recurrent gastric cancer compared to multi-detector computed tomography (MDCT). Fifty patients with histologically (n = 31) or clinically (n = 19) confirmed recurrent gastric cancer underwent both MDCT and [18F]FDG PET/MRI. Two radiologists independently assessed TNM staging using MDCT with and without [18F]FDG PET/MRI and scored resectability using a 5-point confidence scale. Diagnostic performance as assessed by radiologists was compared using McNemar’s test and receiver operating characteristic curve analysis. Of the 50 patients, pathologic T and N staging was available in seven and six patients, respectively. Diagnostic accuracies for T and N staging were not significantly different between MDCT with and without [18F]FDG PET/MRI for both reviewers (p > 0.05). However, for M staging, diagnostic accuracy was significantly improved when 18F-FDG PET/MRI was added to MDCT alone (68.0% [34/50] to 90.0% [45/50] for reviewer 1 [p = 0.001] and 66.0% [33/50] to 96.0% [46/50] for reviewer 2 [p < 0.001]). Regarding the resectability of recurrent gastric cancers, the addition of [18F]FDG PET/MRI increased the area under the curve values for both reviewers (from 0.860 to 0.989 for reviewer 1 and from 0.778 to 0.898 for reviewer 2), with a statistical significance for reviewer 2 (p = 0.002). Compared to MDCT alone, MDCT plus [18F]FDG PET/MRI can improve the diagnostic accuracy for evaluating preoperative M staging as well as resectability for recurrent gastric cancers. • [ 18 F]FDG PET/MRI can improve diagnostic accuracy for preoperative M staging in patients with recurrent gastric cancers. • [ 18 F]FDG PET/MRI can improve diagnostic accuracy for determining resectability in patients with recurrent gastric cancers. • [ 18 F]FDG PET/MRI can provide critical clues for management options for recurrent gastric cancers.