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