Whole-Body Diffusion-Weighted Magnetic Resonance Imaging Is a New Sensitive Non-Invasive Method for Staging and Monitoring Chemotherapy Response of Malignant Lymphoma Including Indolent Lymphoma Compared with FDG-PET/CT

Abstract 4147

Whole-body diffusion-weighted magnetic resonance imaging (DWI-MRI) provides functional information and is able to highlight oncological lesions, but the usefulness has not been established in malignant lymphoma especially for monitoring therapeutic response. Positron emission tomography with fluorine-18 fluorodeoxyglucose (FDG-PET) is a useful imaging producer for tumor staging and therapy monitoring that can visualize active tumor tissue including malignant lymphoma. The spatial resolution of FDG-PET is limited, and low accuracy rates in diabetic patients and those with low grade lymphoma have been reported. We prospectively studied the utility of DWI-MRI with T2 imaging and apparent diffusion coefficient (ADC) for staging and monitoring therapeutic responses in patients with malignant lymphoma compared with FDG-PET/CT. Twenty-eight patients with malignant lymphoma (16 patients with diffuse large B cell lymphoma: DLBCL, 7 with follicular Lymphoma: FL, 3 with aggressive T cell lymphoma: TCL and 2 with Hodgkin lymphoma: HL, including one diabetic patient) received both MRI and FDG-PET examination before (n=28), after 2 courses of chemotherapy (n=25) and one month after the end of chemotherapy (n=9). MRI examination was performed with a 3-Tesla MR system (Signa Excite, Generel Electrics). Whole-body DWI-MRI was performed with echo planar imaging sequence with short T1 inversion recovery (STIR) fat suppression. ADC measurement was performed based on the region of interest (ROI) method. ROI was placed on the lesion showing the highest standardized uptake value (SUV) on FDG-PET/CT scanner (Discovery LS, General Electrics) in each patient, and crucial parameters of the ADC and SUV were compared. Based on staging by PET/CT, 4 patients were clinical stage I, 8 were stage II, 7 were stage III and 9 were stage IV. DWI-MRI findings alone matched PET/CT in 22 patients (79%), whereas these findings combined with T2 imaging increased match in 26 patients (93%). Regarding the early response to chemotherapy, 19 of 25 patients (76%) were considered to show CR on PET/CT and the DWI findings matched PET/CT 23 patients (92%). To evaluate the final response after chemotherapy, 7 of 9 patients (78%) were considered to show CR on PET/CT and the DWI findings matched PET/CT in 8 of 9 patients (89%). Of these nine, one patient with DLBCL who did not show a match was a false positive on PET/CT. In all patients with TCL and HL, the DWI-MRI findings combined with T2 imaging matched PET/CT findings for staging and therapeutic response. Interestingly, the ADC values on DWI-MRI did not differ between DLBCL and FL (0.77 +/− 0.23 and 0.70 +/− 0.08, p=0.99, mean +/− SD respectively), whereas the SUV values of DLBCL on PET/CT were higher than those of FL (14.5 +/− 6.97 and 6.09 +/− 2.54, p < 0.0005, mean +/− SD respectively), suggesting the DWI-MRI could detect the lymphoma lesion more accurately than PET/CT in patients with indolent lymphoma such as FL. We conclude that whole-body DWI-MRI combined with T2 imaging and ADC analysis could be promising sensitive method for staging and therapeutic response evaluation in patients with malignant lymphoma.