2-[¹⁸F]-FDG PET/CT Semiquantitative and Radiomics Predictive Parameters of Richter's Transformation in CLL Patients

Background and Objectives: Chronic lymphocytic leukemia (CLL) is the most common type of leukemia in developed countries, which can evolve into aggressive lymphoma variants, a process called Richter transformation (RT). The aim of this retrospective study was to analyze the role of 2-deoxy-2-[F-18]fluoro-D-glucose positron emission tomography/computed tomography(2-[F-18]-FDG PET/CT) and its semiquantitative and radiomics features in detecting RT and evaluate the impact on overall survival (OS).Materials and Methods: One hundred and thirty-seven patients with histologically proven CLL were retrospectively recruited. PET/CT images were qualitativelyand semiquantitatively examined by estimating the main metabolic parameters (the maximum standardized uptake value body weight (SUVbw), lean body mass (SUVlbm), body surface area(SUVbsa), lesion-to-blood-pool SUV ratio (L-BP SUV R), lesion-to-liver SUV ratio (L-L SUV R),metabolic tumor volume (MTV), and total lesion glycolysis (TLG) and radiomics first- and second-order variables of the lesion with highest uptake. The role of these parameters in predicting RT andOS was analyzed.Results: One hundred and thirty (95%) PET/CT scans were positive, showingan increased tracer uptake at the site of disease, whereas the remaining 7 (5%) scans were negative.SUVbw, SUVlbm, SUVbsa, L-L SUV ratio, and L-BP SUV ratio were significantly higher in the RTgroup (p< 0.001 in all cases). Radiomics first- and second-order features were not significantlyassociated with RT. After a median follow-up of 44 months, 56 patients died; OS was significantlyshorter in patients with RT than patients without RT (28 vs. 34 months;p= 0.002). Binet-stage, RT,and L-BP SUV R were shown to be independent prognostic features.Conclusions: SemiquantitativePET/CT parameters such as SUVbw, SUVlbm, SUVbsa, L-L SUV ratio and L-BP SUV ratio may beuseful in discriminating patients with a high risk of developing RT, whereas Binet-stage, RT, andL-BP SUV R are also significant in predicting OS.