Evaluating 64 Cu-DOTA-rituximab as a PET agent in patients with B-cell lymphoma: a head-to-head comparison with 18 F-fluorodeoxyglucose PET/computed tomography.

Background: This study aimed to evaluate the biodistribution of 64 Cu-DOTA-rituximab and its diagnostic feasibility for lymphoma using CD20-targeted 64 Cu-DOTA-rituximab PET/computed tomography (PET/CT).

Methods: A prospective study involving six patients diagnosed with lymphoma was conducted between January 2022 and January 2023. These patients underwent 18 F-fluorodeoxyglucose ( 18 F-FDG) and 64 Cu-DOTA-rituximab PET/CT scans. 64 Cu-DOTA-rituximab PET/CT images were acquired at 1, 24, and 48 h after administering 64 Cu-DOTA-rituximab to assess the biodistribution and dosimetry over time. The observed lymph nodes were categorized into specific regions, including cervical and supraclavicular, axillary and infraclavicular, mediastinal, hilar, abdominal paraaortic and retroperitoneal, iliac, mesenteric, and inguinal regions, to compare the diagnostic ability of 18 F-FDG and 64 Cu-DOTA-rituximab PET/CT in detecting lymphoma lesions. Furthermore, the tumor-to-background ratio was calculated and compared with the maximum standardized uptake (SUV max ) of the tumors and the mean standardized uptake (SUV mean ) of normal organs. Internal radiation dosimetry was determined using the OLINDA/EXM software.

Results: 64 Cu-DOTA-rituximab uptake in lymph nodes associated with lymphoma progressively increased from 1 to 48 h after injection. In contrast, 64 Cu-DOTA-rituximab uptake in normal organs, such as blood, lung, kidney, bladder, muscle, bone, and brain, decreased over time, whereas it increased in the liver and spleen. When it comes to the comparison between 64 Cu-DOTA-rituximab and 18 F-FDG, the SUV max of tumors was higher on 64 Cu-DOTA-rituximab PET/CT (18.1 ± 8.3) than on 18 F-FDG PET/CT (5.2 ± 1.5). Additionally, the tumor-to-background ratio, measured using the SUV mean of normal muscles, was higher on 64 Cu-DOTA-rituximab PET/CT (55.7 ± 31.0) than on 18 F-FDG PET/CT (8.6 ± 2.8). No adverse events related to 64 Cu-DOTA-rituximab injection were reported.

Conclusion: The results of this study demonstrate the feasibility of using 64 Cu-DOTA-rituximab PET/CT to evaluate the CD20 expression. The increased 64 Cu-DOTA-rituximab uptake in lymph nodes associated with tumors, higher SUV max , and tumor-to-muscle ratios observed with 64 Cu-DOTA-rituximab PET/CT compared with 18 F-FDG PET/CT, highlight the diagnostic potential of this imaging modality.