68Ga-Pentixafor PET/MRI for Treatment Response Assessment in Mantle Cell Lymphoma

Purpose The aim of this study was to compare CXCR4 imaging with 68 Ga-pentixafor PET to MRI for treatment response assessment in patients with mantle cell lymphoma (MCL). Patients and Methods Twenty-two posttreatment 68 Ga-pentixafor PET/MRI scans of 16 patients (7 women and 9 men; mean age, 69.9 ± 7.9) with a total of 67 target lesions on baseline PET/MRI were analyzed. Rates of complete remission per lesion and per scan, according to MRI (based on lesion size) and 68 Ga-pentixafor PET (based on SUV decrease to lower than liver and blood pool uptake), were compared using McNemar tests. The t tests and Pearson correlation coefficients ( r ) were used to compare rates of change in lesion diameter products (DPs) on MRI, and standardized uptake values (SUV max , SUV mean ) on PET, relative to baseline. Results At interim PET/MRI, 18/32 (56.3%) target lesions met CR criteria on 68 Ga-pentixafor PET, and 16/32 (50.0%) lesions met size-based MRI criteria for CR ( P = 0.63). At end-of-treatment PET/MRI, 40/57 (70.2%) target lesions met 68 Ga-pentixafor PET criteria for CR, and 27/57 (47.4%) lesions met size-based MRI criteria for CR ( P = 0.021). Complete remission after treatment was observed more frequently on 68 Ga-pentixafor PET (11/22 scans, 54.5%) than on MRI (6/22 scans, 27.3%) ( P = 0.031). Rates of change did not differ significantly between lesion DP (−69.20% ± 34.62%) and SUV max (−64.59% ± 50.78%, P = 0.22), or DP and SUV mean (−60.15 ± 64.58, P = 0.064). Correlations were strong between DP and SUV max ( r = 0.71, P < 0.001) and DP and SUV mean ( r = 0.73, P < 0.001). Conclusions In MCL patients, 68 Ga-pentixafor PET may be superior for assessment of complete remission status than anatomic MRI using lesion size criteria, especially at the end of treatment.