Diffusion-weighted MRI for staging and evaluation of response in diffuse large B-cell lymphoma: A pilot study

The aim of this study was to compare diffusion-weighted MRI (DW-MRI) with positron emission tomography/computed tomography (PET/CT) for the staging and evaluation of the treatment response in patients with diffuse large B-cell lymphoma (DLBCL). Institutional review board approval was obtained for this study; all subjects gave informed consent. Twelve patients were imaged before treatment and eight of these were also imaged after two cycles of chemotherapy using both DW-MRI and PET/CT. Up to six target lesions were selected at baseline for response assessment based on International Working Group criteria (nodes>1.5cm in diameter; extranodal lesions>1cm in diameter). For pretreatment staging, visual analysis of the numbers of nodal and extranodal lesions based on PET/CT was performed. For interim response assessment after cycle 2 of chemotherapy, residual tumor sites were assessed visually and the percentage changes in target lesion size, maximum standardized uptake value (SUV_max) and apparent diffusion coefficient (ADC) from pretreatment values were calculated. In 12 patients studied pretreatment, there were 46 nodal and 16 extranodal sites of lymphomatous involvement. Agreement between DW-MRI and PET/CT for overall lesion detection was 97% (60/62 tumor sites; 44/46 nodal and 16/16 extranodal lesions) and, for Ann Arbor stage, it was 100%. In the eight patients who had interim assessment, five of their 49 tumor sites remained abnormal on visual analysis of both DW-MRI and PET/CT, and there was one false positive on DW-MRI. Of their 24 target lesions, the mean pretreatment ADC value, tumor size and SUV_max were 772μm²/s, 21.3cm² and 16.9g/mL, respectively. At interim assessment of the same 24 target lesions, ADC values increased by 85%, tumor size decreased by 74% and SUV_max decreased by 83% (all p<0.01 versus baseline). DW-MRI provides results comparable with those of PET/CT for staging and early response assessment in patients with DLBCL.