Diffusion-weighted MRI for initial staging in Hodgkin`s lymphoma: comparison with FDG PET

To evaluate the use of diffusion-weighted MRI (DWI) for initial staging of Hodgkin`s lymphoma and compare it to FDG PET.

Forty-one patients with Hodgkin`s lymphoma (14 f, 27 m, median age 39 y) were included in this retrospective study. All patients underwent FDG PET/MR for initial staging, including DWI. The Lugano classification was used to describe disease extent. A combination of follow-up imaging and histopathology served as the reference standard. Method agreement was assessed using weighted kappa (κ). The accuracy of the imaging methods was evaluated using ROC curve analysis.

Regarding the Lugano stage, DWI and FDG PET had identical results in 34/41 cases (κ = 0.77). Sensitivity and specificity for nodal involvement was 89.9% and 93.8% for DWI, and 93.8% and 86.9% for FDG PET, respectively. In regard to extranodal involvement, sensitivity and specificity were 88.5% and 99.3% for DWI and 92.3% and 92.7% for FDG PET. The accuracy of both methods for nodal (p = 0.06) and extranodal involvement (p = 0.66) did not differ significantly.

Despite high sensitivity and specificity, DWI in free breathing cannot be currently recommended as an alternative to FDG PET in initial staging of Hodgkin`s lymphoma due to substantial differences in regard to therapy-determining Lugano Stage.