Abstract
Background: In recent years, molecular imaging adressing the C-X-C motif chemokine receptor 4 (CXCR4) has increasingly been utilized in various clinical settings. Here, we aimed to assess radiopharmaceutical uptake and image contrast to determine the most relevant clinical applications for CXCR4-directed imaging. We also investigated the impact of specific activity on scan contrast. Methods: 690 patients with a variety of neoplasms underwent a total of 777 PET/CT scans with 68Ga-PentixaFor, serving as CXCR4-specific radioligand. A semiquantitative target lesion (TL) analysis was conducted [providing maximum standardized uptake values (SUVmax) and target-to-blood pool ratio (TBR), defined as SUVmax (from TL) divided by mean SUV (from blood pool)]. The applied specific activity (in MBq/µg) was compared to semi-quantitative assessments. Results: Of the 777 scans, 242 did not show discernible uptake in disease sites, leaving 535 PET scans (68.9%) for further analysis. Very high tracer uptake (SUVmax > 12) was found in multiple myeloma (MM; n = 113), followed by adrenocortical carcinoma (n = 30), mantle cell lymphoma (MCL; n = 20), adrenocortical adenoma (n = 6) and small cell lung cancer (SCLC; n = 12). Providing information on image contrast, comparable results for TBR were recorded, with TBR (>8) in MM, MCL and acute lymphoblastoid leukemia (n = 6). When comparing specific activity with semiquantitative parameters, no significant correlation was found for SUVmax or TBR (P ≥ 0.612). Conclusion: In this large cohort, 68Ga-PentixaFor demonstrated high image contrast in a variety of neoplasms, particularly for hematologic malignancies, SCLC and adrenocortical neoplasms. The present analysis may provide a roadmap to detect patients who may benefit from CXCR4-targeted therapies.
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