Trop2-targeted PET/CT with ⁶⁸ Ga-MY6349 for detecting metastatic lesions in metastatic thyroid cancer: Prospective comparison of diagnostic accuracy with ¹⁸ F-FDG PET/CT.

6104 Background: Trophoblast cell surface antigen 2 (Trop2) targeted molecular imaging with 68 Ga-MY6349 has been proposed as a potential modality for visualizing cancerous lesions, but its utility for identifying metastatic thyroid cancer (TC) is not well-established in the literature. This study aims to evaluate the clinical utility of 68 Ga‐MY6349 PET/CT for detecting metastatic TC and to compare the results with those of 18 F‐fluorodeoxyglucose (FDG) PET/CT. Methods: This was a prospective, single-center, open-labeled, single-arm comparative imaging trial. Patients with clinically suspected or confirmed metastatic TC were prospectively enrolled and underwent paired 68 Ga‐MY6349 and 18 F‐FDG PET/CT from November 2023 to January 2024. Histopathology and clinical follow-up (mean 12 months ± 0.7 [standard deviation] (range: 11-13 months) were used as reference standards for the final diagnosis. 18 F-FDG and 68 Ga-MY6349 uptake were compared by using the Wilcoxon signed-rank test. The McNemar test was used to compare the diagnostic efficacy of the two techniques, and the influence of various clinicopathological characteristics on 18 F-FDG and 68 Ga-MY6349 uptake was evaluated by Mann-Whitney and Kruskal-Wallis tests. Results: In total, 55 participants (median age, 51 years [interquartile range, 35-61 years]; 17 men) were evaluated. In all 55 participants, the 68 Ga-MY6349-derived SUV max was higher than the 18 F-FDG-derived SUV max in the local recurrence (24.9 vs. 10.7, P = .026), metastatic central compartment (12.7 vs. 4.9, P < .001), metastatic lateral compartment (11.0 vs. 5.4, P < .001), and mediastinal lymph nodes (LNs) (9.5 vs. 4.6, P = .012). 68 Ga-MY6349 PET/CT had a higher sensitivity than 18 F-FDG PET/CT for detecting neck lesions (88% vs. 56%; P < .001). Conclusions: 68 Ga-MY6349 PET/CT was superior to 18 F-FDG PET/CT for detecting metastatic TC, especially in local recurrence and LNs metastases. Clinical trial information: NCT06465017 . Comparison of 18 F-FDG and 68 Ga-MY6349 uptake in metastatic thyroid cancer. Site of Disease 18 F-FDG Uptake(SUV max) 68 Ga-MY6349 Uptake(SUV max) P value Local recurrence 10.7±7.6 24.9±23.7 0.026 Central compartment LNs 4.9±4.6 12.7±10.9 <0.001 Lateral compartment LNs 5.4±6.4 11.0±10.23 <0.001 Mediastinal LNs 4.6±2.8 9.5±7.5 0.012 Pulmonary metastases 2.4±0.7 3.4±1.5 0.175 Other sites* 8.5±3.8 14.2±17.1 0.691 LNs, lymph nodes; Other sites include bone and subcutaneous metastasis.