Role of WB-MR/DWIBS compared to 18F-FDG PET/CT in the therapy response assessment of lymphoma

Introduction: This study prospectively evaluated whole-body magnetic resonance/diffusion-weighted imaging with body signal suppression (WB-MR/DWIBS) reliability compared to 18F-FDG PET/CT in the treatment response assessment of classic Hodgkin lymphomas (HL) and aggressive non-Hodgkin lymphomas (aNHL). Materials and methods: Twenty-seven consecutive patients were prospectively enrolled at the time of diagnosis. Eighteen (11 HL and seven aNHL) were considered for the analysis. They received chemo/radiotherapy as induction and completed post-treatment evaluation performing both 18F-FDG PET/CT and WB-MR/DWIBS. The revised response criteria for malignant lymphomas were used to assess the response to treatment. We evaluated the agreement between the two methods by Cohen’s K test. Post-therapy WB-MR/DWIBS sensitivity, specificity, PPV, NPV and accuracy were then calculated, considering the 12 months of follow-up period as the gold standard. Results: By using an evaluation on a lesion-by-lesion basis, WB-MR/DWIBS and 18F-FDG PET/CT showed an overall good agreement (K = 0.796, 95 % IC = 0.651–0.941), especially in the evaluation of the nodal basins in aNHL (K = 0.937, 95 % IC = 0.814–1). In reference to the revised response criteria for malignant lymphomas, the two methods showed a good agreement (K = 0.824, 95 % IC = 0.493–1). Post-therapy sensitivity, specificity, PPV, NPV and accuracy of WB-MR/DWIBS were 43, 91, 75, 71 and 72 %, respectively. Conclusion: WB-MR/DWIBS seems to be an appropriate method for the post-treatment assessment of patients affected by HL and aNHL. The small discrepancies between the two methods found within HL could be due to the biological and metabolic behavior of this group of diseases. Larger prospective studies are necessary to better define the role of WB-MR/DWIBS in this setting of patients.