18F-FDG-PET/MRI in preoperative staging of oesophageal and gastroesophageal junctional cancer

Abstract

To evaluate integrated 2-[18F]-fluoro-2-deoxy-d-glucose (18F-FDG) positron-emission tomography (PET)/magnetic resonance imaging (MRI), in comparison with the standard technique, integrated 18F-FDG-PET/computed tomography (CT), in preoperative staging of oesophageal or gastroesophageal junctional cancer. In the preoperative staging of 16 patients with oesophageal or gastroesophageal junctional cancer, 18F-FDG-PET/MRI was performed immediately following the clinically indicated 18F-FDG-PET/CT. MRI-sequences included T1-weighted fat-water separation (Dixon's technique), T2-weighted, diffusion-weighted imaging (DWI), and gadolinium contrast-enhanced T1-weighted three-dimensional (3D) imaging. PET was performed with 18F-FDG. Two separate teams of radiologists conducted structured blinded readings of 18F-FDG-PET/MRI or 18F-FDG-PET/CT, which were then compared regarding tumour measurements and characteristics as well as assessment of inter-rater agreement (Cohen's kappa) for the clinical tumour, nodal and metastatic (TNM) stage. There were no medical complications. Comparison of tumour measurements revealed high correlations without significant differences between modalities. The maximum standardised uptake value (SUVmax) values of the primary tumour with 18F-FDG-PET/MRI had excellent correlation to those of 18F-FDG-PET/CT (0.912, Spearman's rho). Inter-rater agreement between the techniques regarding T-stage was only fair (Cohen's kappa, 0.333), arguably owing to relative over-classification of the T-stage using 18F-FDG-PET/CT. Agreements in the assessment of N- and M-stage were substantial (Cohen's kappa, 0.849 and 0.871 respectively). Preoperative staging with 18F-FDG-PET/MRI is safe and promising with the potential to enhance tissue resolution in the area of interest. 18F-FDG-PET/MRI and 18F-FDG-PET/CT correlated well for most of the measured values and discrepancies were seen mainly in the assessment of the T-stage. These results facilitate further studies investigating the role of 18F-FDG-PET/MRI in, e.g., predicting or determining the response to neoadjuvant therapy.