Whole-Body MRI versus an FDG-PET/CT-Based Reference Standard for Early Response Assessment and Restaging of Paediatric Hodgkin's Lymphoma: A Prospective Multicentre Study

Abstract

Background and Aims: To compare WB-MRI with an FDG-PET/CT-based reference for early response assessment and restaging in children with Hodgkin's lymphoma (HL). Methods: 51 children (ages 10-17) with HL were included in this prospective, multicentre study. All participants underwent WB-MRI and FDG-PET/CT at early response assessment. 13 of the 51 patients also underwent both WB-MRI and FDG-PET/CT at restaging. Two radiologists independently evaluated all WB-MR images in two separate readings: without and with DWI. The FDG-PET/CT examinations were evaluated by a nuclear medicine physician. An expert panel assessed all discrepancies between WB-MRI and FDG-PET/CT to derive the FDG-PET/CT-based reference standard. Inter-observer agreement for WB-MRI was calculated using kappa statistics. Concordance, PPV, NPV, sensitivity and specificity for correct assessment of the response between WB-MRI and the reference standard were calculated for both nodal and extra-nodal disease presence and total response evaluation. Results: Inter-observer agreement of WB-MRI including DWI between both readers was moderate (κ 0.46-0.60). For early response assessment, WB-MRI DWI agreed with the reference standard in 33/51 patients (65%, 95%CI 51-77%) versus 15/51 (29%, 95%CI 19-43%) for WB-MRI without DWI. For restaging, WB-MRI including DWI agreed with the reference standard in 9/13 patients (69%, 95%CI 42-87%) versus 5/13 patients (38%, 95%CI 18-64%) for WB-MRI without DWI. Conclusions: The addition of DWI to the WB-MRI protocol in early response assessment and restaging of paediatric HL improved agreement with the FDG-PET/CT-based reference standard. However, WB-MRI remained discordant in 30% of the patients compared to standard imaging for assessing residual disease presence.