The study was completed as planned after achieving the target enrollment and completing all protocol-specified procedures and follow-up.

In this study, we comprehensively evaluated the clinical utility of Trop2 PET/CT (68Ga-MY6349 PET/CT) imaging for detecting recurrent and metastatic thyroid cancer, and the results were compared with those of 18F-FDG PET/CT. The primary objective of this study was to evaluate the patient-based sensitivity of 68Ga-MY6349 PET/CT in detecting recurrent and metastatic thyroid cancer. The secondary objectives included its overall specificity, lesion-based diagnostic performance, comparative tumor uptake relative to 18F-FDG PET/CT, safety profile, and the impact on clinical management.

Trophoblast cell-surface antigen 2 (Trop2), a transmembrane glycoprotein, is highly expressed in most epithelial cancers but has low expression in most normal tissues. Notably, Trop2 expression is significantly elevated in thyroid cancer, representing an important molecular hallmark of thyroid cancer. Previously, we developed a Trop2-specific radiotracer for PET/CT imaging, 68Ga-MY6349, with the potential for clinical translation across various cancer types. In particular, 68Ga-MY6349 PET/CT demonstrated the highest tumor uptake in PTC across 15 cancer types, enabling visualization of more metastatic lesions than conventional 18F-FDG PET/CT.

In this study, we comprehensively evaluated the clinical utility of Trop2 PET/CT imaging for detecting recurrent and metastatic thyroid cancer, and the results were compared with standard-of-care imaging (18F-FDG PET/CT). The primary objective of this study was to evaluate the patient-based sensitivity of 68Ga-MY6349 PET/CT in detecting recurrent and metastatic thyroid cancer. The secondary objectives included its overall specificity, lesion-based diagnostic performance, comparative tumor uptake relative to 18F-FDG PET/CT, safety profile, and the impact on clinical management.

Inclusion Criteria:

• Adult patients (aged 18 years or older);
• Patients with a history of previously treated thyroid cancer, including DTC and HGFCTC following thyroidectomy with or without 131I therapy, MTC after thyroidectomy, or ATC; either (1) evidence of structural or suspicious lesions on standard of care imaging or (2) biochemical evidence of disease in the absence of structural findings, defined as elevated thyrotropin suppressed thyroglobulin (Tgon ≥1 ng/mL after 131I ablation or ≥5 ng/mL without ablation) with negative anti thyroglobulin antibodies (<20 IU/mL) for DTC and HGFCTC or elevated calcitonin (>10 pg/mL) for MTC;
• Patients who had scheduled both standard-of-care imaging (18F-FDG PET/CT) and 68Ga-MY6349 scans;
• Patients who were able to provide informed consent (signed by participant, parent or legal representative) and assent according to the guidelines of the Clinical Research Ethics Committee.
• No other anticancer therapy within four weeks prior to PET imaging.

Exclusion Criteria:

• Patients with pregnancy or lactating;
• Patients had a second primary tumor;
• The inability or unwillingness of the research participant, parent, or legal representative to provide written informed consent.