Early Treatment Response Evaluation in Patients with Diffuse Large B-Cell Lymphoma-A Pilot Study Comparing Volumetric MRI and PET/CT

The purpose of this study is to evaluate the time course of early chemotherapy response in patients with aggressive non-Hodgkin's lymphoma (NHL) by magnetic resonance imaging (MRI) and positron emission tomography/computed tomography (PET/CT). Eight patients with histologically proven aggressive NHL were imaged by MRI and PET/CT before treatment (E1), 1 week (E2), and two cycles (E3) after chemotherapy. The mean tumor volume on MRI was 276 mL at baseline; it decreased 58% at E2 (p < 0.05) and 65% further at E3 (p < 0.05), giving a total decrease of 84% (p < 0.05). All the imaged pre-therapy tumors were strongly positive on PET/CT, with a mean maximum standardized uptake value (SUV(max)) of 20. The SUV(max) decreased 60% at E2 (p < 0.05) and 59% further at E3 (p < 0.05), giving a total decrease of 83% (p < 0.05). The active tumor burden (mean 229 mL) decreased 66% at E2 (p < 0.05). The tumor volume on MRI correlated with the active tumor volume on fused PET/CT images in the same region of interest at both E1 and E2 (r = 0.88, p < 0.01, respectively). Standard chemotherapy causes rapid decrease of both tumor metabolic activity and volume as early as 1 week, which continues to decline during therapy. Both volumetric MRI and PET/CT are valuable tools for early treatment response evaluation of aggressive NHL.