Short Communication: (18)F-immuno-PET: Determination of anti-CD66 biodistribution in a patient with high-risk leukemia.

The monoclonal antibody anti-CD66 labeled with (99m)Tc is widely used as Scintimun granulocyte for bone marrow immunoscintigraphy. Further, recently performed clinical radioimmunotherapy studies with [(90)Y]Y-anti-CD66 proved to be suitable for the treatment of hematologic malignancies. Before radioimmunotherapy with [(90)Y]Y-anti-CD66, dosimetric estimations are required to minimize radiotoxicity and determine individual applicable activities. Planar imaging, using gamma-emitting radionuclides, is conventionally carried out to estimate the absorbed organ doses. In contrast, immuno-PET (positron emission tomography) enables the quantification of anti-CD66 accumulation and provides better spatial and temporal resolution. Therefore, in this study, a semiautomated radiosynthesis of [(18)F]F-anti-CD66 was developed, using the (18)F-acylation agent, N-succinimidyl-4-[(18)F]fluorobenzoate ([(18)F]SFB). As a proof of concept, an intraindividual comparison between PET and conventional scintigraphy, using (18)F- and (99m)Tc-labeled anti-CD66 in 1 patient with high-risk leukemia, is presented. Both labeled antibodies displayed a similar distribution pattern with high preferential uptake in bone marrow. Urinary excretion of [(18)F]F-anti-CD66 was increased and bone marrow uptake reduced, in comparison to [(99m)Tc]Tc-anti-CD66. Nevertheless, PET-based dosimetry with [(18)F]F-anti-CD66 could provide additional information to support conventional scintigraphy. Moreover, [(18)F]F-anti-CD66 is ideally suited for bone marrow imaging using PET.