Evaluation of the specificity of [18F]fludarabine PET/CT in a xenograft model of follicular lymphoma: comparison with [18F]FDG and impact of rituximab therapy

Background [ 18 F]Fludarabine is a novel positron emission tomography (PET) radiotracer for imaging lymphoma. The purpose of this preclinical study was to evaluate the robustness of [ 18 F]fludarabine during rituximab therapy. In addition, a comparison was made between [ 18 F]fludarabine and [ 18 F]fluorodeoxyglucose ([ 18 F]FDG) with regard to their concordance with histologically derived data. Methods CB17-SCID mice bearing human follicular DOHH-2 lymphoma were treated once weekly with rituximab (10 mg/kg) or physiological saline over 3 weeks. To obtain the tracer uptake in the metabolically active volume of the tumour (MAVT), a background-level threshold was applied to the volume of interest (VOI) defined on computed tomography (CT) image. The tumour uptake analysis was performed with MAVT-based segmentation for data analysis of sequential [ 18 F]fludarabine PET/CT studies and with total tumour-based segmentation for comparison with histologically derived data. Results The correlation between the MAVT and [ 18 F]fludarabine accumulation (%ID) in those viable tissues was equally significant for both vehicle- or rituximab-treated mice; for these latter, the presence of lymphoid tissues at the end of imaging sessions was confirmed histologically. A stronger correlation was demonstrated between quantitative values extracted from [ 18 F]fludarabine-PET and histology ( r 2 = 0.91, p