Whole body magnetic resonance with diffusion weighted sequence with body signal suppression compared to (18)F-FDG PET/CT in newly diagnosed lymphoma.

Lymphomas are a heterogeneous group of lymphoid malignancies, which can be broadly divided into non-Hodgkin Lymphomas (NHL) and Hodgkin lymphoma (HL) that display different patterns of biological behavior and response to treatment. Their incidence is still increasing and for this reason they require a lot of effort in scientific research. The management of both NHL and HL follows well-established guidelines based on the initial staging assessment. Therefore an accurate staging is the basis for the selection of an appropriate therapeutic approach in order to prevent over or under treatment as well as to minimize morbidity related to the radio-chemotherapy regimens given. (18)F-FDG-PET is currently regarded as the reference standard imaging modality in the staging of the majority of lymphoma type, for evaluation of distribution of the disease by providing both functional and anatomic information in a single whole body examination. In particular its role is established in HL and high-grade NHL, confirmed also in Follicular Lymphoma, but its impact on the other histotypes remains to be demonstrated. Among the diagnostic tools currently available for a bio-molecular imaging assessment, of great interest is the Whole Body-Magnetic Resonance with DWIBS sequence (WB-MR/DWIBS), an emerging and promising functional whole body imaging modality to evaluate oncologic and non-oncologic lesions, resulting in images that remarkably resemble (18)F-FDG PET/CT studies. In our research study we evaluated the role of WB-MR/DWIBS, compared with (18)F-FDG-PET/CT in the initial staging of lymphomas, considering its impact on the management of these patients and how it could influence the therapeutic choice. We prospectively enrolled 27 consecutive patients with newly diagnosed lymphoma (13 HL, 14 NHL) histologically proven, who underwent (18)F-FDG-PET/CT and WB-MR/DWIBS (coronal T1-weighted, coronal STIR, axial sequences DWIBS) within 10 days from the diagnosis and before start the treatment. We evaluated the overall agreement between the two methods, the general agreement in evaluating both nodal and extra-nodal involvement and a specific site agreement according to lymph nodal basins or extra-nodal sites involvement. The agreement between the two diagnostic tools in relation to histological types (HL/NHL) and in relation to indolent and aggressive forms, within NHL histotypes, as well as in relation to the Ann Arbor stage was also evaluated. We also analyzed the role of WB-MRI/DWIBS and (18)F-FDG-PET/CT in bone marrow involvement detection by calculating their sensitivity and specificity, with bone marrow biopsy as the reference standard, and comparing them with McNemar test. A total of 85 lesions, nodal (74) and extra-nodal (11), were detected by (18)F-FDG-PET/CT. WB-MRI/DWIBS showed a total of 91 sites involved, (81) nodal and (13) extra-nodal lesions. The overall agreement between the two imaging modalities was very good (k=0.815; IC:0.739-0.890); however considering histotypes, the agreement comes down to good in evaluating NHL for both nodal and extra-nodal involvement (k=0.763, IC: 0.627-0.898; k=0.629, IC:-0.021-1.278). Considering indolent or aggressive forms the agreement between WB-MR/DWIBS and (18)F-FDG PET/CT findings was very good in aggressive forms while it appeared to be lower in indolent forms. Sensitivity and specificity of WB-MRI/DWIBS and (18)F-FDG PET/CT in bone marrow involvement detection were respectively: 100%and 100% vs. 50% and 96%. The switch from (18)F-FDG PET/CT to WB-MR/DWIBS in the AA Staging System resulted in an over-staging in 1/27 patient. The two methods were concordant in the staging in 26/27 patients (96%). In conclusion, our initial results show a good overall agreement between the two diagnostic tools. (18)F-FDG-PET/CT remains the gold standard for lymphoma staging, however WB-MRI/DWIBS can be useful in histotypes not (18)F-FDG-avid or in the evaluation of "critical" organs for (18)F-FDG PET/CT. The integrated information provided by metabolic and tissutal functional imaging can be complementary to assist hematologic decision of tailored patient's treatment.