Comparison of diffusion-weighted MRI and [18F]FDG PET/MRI for treatment monitoring in pediatric Hodgkin and non-Hodgkin lymphoma

ObjectiveTo compare tumor therapy response assessments with whole-body diffusion-weighted imaging (WB-DWI) and 18F-fluorodeoxyglucose ([F-18]FDG) PET/MRI in pediatric patients with Hodgkin lymphoma and non-Hodgkin lymphoma.Materials and methodsIn a retrospective, non-randomized single-center study, we reviewed serial simultaneous WB-DWI and [F-18]FDG PET/MRI scans of 45 children and young adults (27 males; mean age, 13 years & PLUSMN; 5 [standard deviation]; age range, 1-21 years) with Hodgkin lymphoma (n = 20) and non-Hodgkin lymphoma (n = 25) between February 2018 and October 2022. We measured minimum tumor apparent diffusion coefficient (ADCmin) and maximum standardized uptake value (SUVmax) of up to six target lesions and assessed therapy response according to Lugano criteria and modified criteria for WB-DWI. We evaluated the agreement between WB-DWI- and [F-18]FDG PET/MRI-based response classifications with Gwet's agreement coefficient (AC).ResultsAfter induction chemotherapy, 95% (19 of 20) of patients with Hodgkin lymphoma and 72% (18 of 25) of patients with non-Hodgkin lymphoma showed concordant response in tumor metabolism and proton diffusion. We found a high agreement between treatment response assessments on WB-DWI and [F-18]FDG PET/MRI (Gwet's AC = 0.94; 95% confidence interval [CI]: 0.82, 1.00) in patients with Hodgkin lymphoma, and a lower agreement for patients with non-Hodgkin lymphoma (Gwet's AC = 0.66; 95% CI: 0.43, 0.90). After completion of therapy, there was an excellent agreement between WB-DWI and [F-18]FDG PET/MRI response assessments (Gwet's AC = 0.97; 95% CI: 0.91, 1).ConclusionTherapy response of Hodgkin lymphoma can be evaluated with either [F-18]FDG PET or WB-DWI, whereas patients with non-Hodgkin lymphoma may benefit from a combined approach.