18F-FDG PET/MRI for restaging esophageal cancer after neoadjuvant chemoradiotherapy

Purpose The purpose of this study was to investigate whether 18F-fluorodeoxyglucose (F-18-FDG) PET/MRI may potentially improve tumor detection after neoadjuvant chemoradiotherapy (nCRT) for esophageal cancer.Methods This was a prospective, single-center feasibility study. At 6-12 weeks after nCRT, patients underwent standard F-18-FDG PET/computed tomography (CT) followed by PET/MRI, and completed a questionnaire to evaluate burden. Two teams of readers either assessed the F-18-FDG PET/CT or the F-18-FDG PET/MRI first; the other scan was assessed 1 month later. Maximum standardized uptake value corrected for lean body mass (SULmax) and mean apparent diffusion coefficient (ADC(mean)) were measured at the primary tumor location. Histopathology of the surgical resection specimen served as the reference standard for diagnostic accuracy calculations. When patients had a clinically complete response and continued active surveillance, response evaluations until 9 months after nCRT served as a proxy for ypT and ypN (i.e. 'ycT' and 'ycN').Results In the 21 included patients [median age 70 (IQR 62-75), 16 males], disease recurrence was found in the primary tumor in 14 (67%) patients (of whom one ypM+, detected on both scans) and in locoregional lymph nodes in six patients (29%). Accuracy (team 1/team 2) to detect yp/ycT+ with F-18-FDG PET/MRI vs. F-18-FDG PET/CT was 38/57% vs. 76/61%. For ypN+, accuracy was 63/53% vs. 63/42%, resp. Neither SULmax (both scans) nor ADC(mean) were discriminatory for yp/ycT+ . Fourteen of 21 (67%) patients were willing to undergo a similar F-18-FDG PET/MRI examination in the future.Conclusion F-18-FDG PET/MRI currently performs comparably to F-18-FDG PET/CT. Improvements in the scanning protocol, increasing reader experience and performing serial scans might contribute to enhancing the accuracy of tumor detection after nCRT using F-18-FDG PET/MRI.Trial registration Netherlands Trial Register NL9352.