Session Type: Poster Session C
Session Time: 9:00AM-11:00AM
Background/Purpose: 2-[18F]fluoro-2-deoxy-D-glucose(FDG) is the reference PET radiotracer for detecting inflammation in giant cell arteritis (GCA). C-X-C motif chemokine receptor 4 (CXCR4)-directed PET, however, allows for targeting leukocyte subsets, thereby providing a direct visualization of active inflammation. We aimed to report initial results from a Phase II trial applying chemokine receptor-targeted imaging in patients with newly diagnosed GCA (NCT05604482).
Methods: Nine treatment-naïve individuals with confirmed GCA underwent PET/CT imaging with both FDG and [68Ga] PentixaFor (PXF). For each PET, a total of 13 arterial segments per patient were analyzed. In addition, eight joints were examined for concurrent polymyalgia rheumatica. We compared both scans on a visual (using PETVAS) and quantitative level (by calculating the target-to-background ratio [TBR], with blood pool as reference). Flow cytometry determined quantitative CXCR4 expression on leukocytes in peripheral blood by calculating a normalized median fluorescence intensity (NMFI) scoring (with CXCR4 antibody isotype serving as control). Quantitative PET results were then correlated with NMFI.
Results: At the visual level, PETVAS of FDG (25.62 ± 5.61) was comparable with PXF (21.33 ± 3.5, P=0.07). The TBR of FDG (2.41 ± 0.96) was also not significantly different from that of PXF (1.8 ± 0.8, P=0.11). The interquartile ranges (IQR) for PEN (IQR, 0.48), however, were lower than for FDG (IQR, 1.5), suggesting lower scatter and improved accuracy for PXF-based quantitative read-outs. Comparable results were also recorded for joints (PEN: IQR, 0.25; FDG: IQR, 0.5). Flow cytometry showed broad expression of CXCR4 on leukocytes. Subpopulations with the highest CXCR4 expression were naive B and T cells, followed by basophils. NMFI and PXF-based quantification showed significant correlations with basophils in the aorta, with the most prominent association for the abdominal segment (r=0.85, P=0.03).
Conclusion: Quantification of the CXCR4-targeted PET radiotracer PXF was comparable to FDG for assessing vessel wall and joint inflammation. Thus, PXF PET may be incorporated for image-guided, anti-inflammatory strategies in patients with newly diagnosed GCA.
To cite this abstract in AMA style:Froehlich M, Serfling S, Gernert M, Guggenberger K, Higuchi T, Samnick S, Schmalzing M, Buck A, Bley T, Werner R. C-X-C Motif Chemokine Receptor 4-targeted Molecular Imaging in Giant Cell Arteritis – a Head-to-head Comparison with FDG PET [abstract]. Arthritis Rheumatol. 2023; 75 (suppl 9). https://acrabstracts.org/abstract/c-x-c-motif-chemokine-receptor-4-targeted-molecular-imaging-in-giant-cell-arteritis-a-head-to-head-comparison-with-fdg-pet/. Accessed .
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ACR Meeting Abstracts - https://acrabstracts.org/abstract/c-x-c-motif-chemokine-receptor-4-targeted-molecular-imaging-in-giant-cell-arteritis-a-head-to-head-comparison-with-fdg-pet/