Ga-Pentixafor PET/MRI for CXCR4 Imaging of Chronic Lymphocytic Leukemia: Preliminary Results

Objectives This prospective proof-of-principle study aimed to determine whether [⁶⁸Ga]Ga-Pentixafor uptake, which reflects CXCR4 expression, is higher in the bone marrow of chronic lymphocytic leukemia (CLL) than in other oncological diseases without bone marrow infiltration and can therefore be used for CLL imaging. Materials and Methods Thirteen CLL patients and 20 controls (10 with pancreatic adenocarcinoma and 10 with mucosa-associated lymphoid tissue lymphoma) with histologically proven cancer underwent [⁶⁸Ga]Ga-Pentixafor positron emission tomography/magnetic resonance imaging. Standardized [⁶⁸Ga]Ga-Pentixafor uptake values (SUV_max, SUV_mean) were measured in the bone marrow of the pelvis, the lumbar vertebra L4, and the bony structure with the visually highest tracer uptake ("hottest lesion"). Mean apparent diffusion coefficient values were also measured in the pelvis. Serum leukocyte count (gram per liter), lymphocyte percentage (percent), lactate dehydrogenase (unit per liter), β2-microglobulin (milligram per deciliter), and C-reactive protein (milligram per deciliter) were measured. Statistical analyses comprised analysis of variance with Games-Howell post hoc tests and Spearman correlation coefficients. Results SUV_max and SUV_mean differed significantly between CLL and pancreatic adenocarcinoma in the pelvis (P = 0.032 and P = 0.008) and lumbar vertebra L4 (both P < 0.001). SUV_mean also differed in the pelvis (P = 0.020) and L4 (P = 0.041), and SUV_max in L4 (P = 0.019), between CLL and mucosa-associated lymphoid tissue lymphoma. Receiver operating characteristic-based areas under the curve for separation of CLL from the control groups were greatest for the SUV_max of the bony structure with the strongest [⁶⁸Ga]Ga-Pentixafor uptake (0.94) and the SUV_max of L4 (0.92). There was no significant correlation between [⁶⁸Ga]Ga-Pentixafor uptake and pelvic apparent diffusion coefficients or serum parameters. Conclusions [⁶⁸Ga]Ga-Pentixafor positron emission tomography/magnetic resonance imaging may possibly be useful for CXCR4-based CLL imaging.