PROSPECTIVE STUDY OF 3T WHOLE BODY DIFFUSION WEIGHTED MAGNETIC RESONANCE (WB DWI MRI) COMPARED TO PET IN STAGING AND ASSESSMENT OF TREATMENT RESPONSE IN FDG AVID LYMPHOMAS

Abstract

Introduction: PET is considered the gold standard for staging and evaluation of treatment response in FDG avid Lymphoma. 3T WB-DWI-MRI may represent an option for detection and better characterisation of tumoral lesions without use of FDG or iodated/paramagnetic contrast medium. We compared 3T WB-DWI-MRI with PET in the evaluation of Hodgkin lymphoma (HL) and Diffuse large cell lymphoma patients (DLBCL). Methods: From may 2016, 25 patients (14 cases of HL and 11 cases of DLBCL) were diagnosed at our institution. PET and 3T WB-DWI-MRI was perfomed at diagnosis and post treatment for a total of 118 nodal sites and 21 extranodal valued sites. DWI imaging was obtained with multi shot sequences (thickness 4 mm) multi-b (b-value: 0, 150, 1000) and ADC cut off value 1.2 for functional evaluation. Morphological images were obtained by using sequences fast spin-echo short time inversion recovery (STIR with thickness 4mm) and Turbo spin-echo (T2-TSE with thickness 4mm) and sequnces T1-FAST-Field-echo (T1-FFE) in and out - phase (thickness 4mm). MRI were compared with PET imaging performed at the same time and assessed blind by radiologist and Nuclear Medicine physician. Results: The 3T WB-DWI-MRI and PET results were concordant at the diagnosis after evaluation of 118 nodal site and 21 extra nodal site with Cohen's Kappa coefficient showed agreement to be excellent (K = 0.82 and 0.84 respectively). When performed after treatment the two methods were not concordant due to the greater sensitivity and specificity of the RMI (high positive and negative predictive value. In 5/25 cases of nodal site and in 2/16 cases of extra nodal site after chemotherapy MRI and PET results were discordant and PET failed complete remission finding (doubts residues after therapy not confirmed at subsequent follow-up). Conclusions: These data suggest that 3T WB-DWI-MRI can be considered a sensitive and specific method for assessing treatment response in Lymphoma without the use of ionising radiation or administration of F-18 Flurodeoxyglucose. In this population, MRI appears to obtain a better definition of the response after chemotherapy especially in mediastinal, hepatic, waldeyer ring and bone sites. Further studies are needed to evaluate the optimum ADC values in assessing treatment response in a more large number of patients. Keywords: diffuse large B-cell lymphoma (DLBCL); Hodgkin lymphoma (HL); positron emission tomography (PET).