super(18)F-Immuno-PET: Determination of Anti-CD66 Biodistribution in a Patient with High-Risk Leukemia

The monoclonal antibody anti-CD66 labeled with super(99m)Tc is widely used as Scintimun registered granulocyte for bone marrow immunoscintigraphy. Further, recently performed clinical radioimmunotherapy studies with [ super(90)Y]Y-anti-CD66 proved to be suitable for the treatment of hematologic malignancies. Before radioimmunotherapy with [ super(90)Y]Y-anti-CD66, dosimetric estimations are required to minimize radiotoxicity and determine individual applicable activities. Planar imaging, using y-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 [ super(18)F]F-anti-CD66 was developed, using the super(18)F-acylation agent, N-succinimidyl-4-[ super(18)F]fluorobenzoate ([ super(18)F]SFB). As a proof of concept, an intraindividual comparison between PET and conventional scintigraphy, using super(18)F- and super(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 [ super(18)F]F-anti-CD66 was increased and bone marrow uptake reduced, in comparison to [ super(99m)Tc]Tc-anti-CD66. Nevertheless, PET-based dosimetry with [ super(18)F]F-anti-CD66 could provide additional information to support conventional scintigraphy. Moreover, [ super(18)F]F-anti-CD66 is ideally suited for bone marrow imaging using PET.