Trophoblast Cell-Surface Antigen 2 (Trop-2) Targeted PET/CT in Recurrent and Metastatic Thyroid Cancer

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 evaluated the diagnostic performance of 68Ga-MY6349 PET/CT in recurrent and metastatic thyroid cancer and compared it with 18F-FDG PET/CT. The results demonstrated that 68Ga-MY6349 PET/CT was superior to 18F-FDG PET/CT for lesion detection, particularly in patients with PTC and TENIS. In addition, fibroblast activation protein is highly expressed in cancer-associated fibroblasts in thyroid cancer. 68Ga-labeled FAP inhibitor (FAPI) has demonstrated favorable in vivo pharmacokinetics and higher diagnostic accuracy than 18F-FDG in various types of cancers, including thyroid cancer.

In this study, we comprehensively evaluated the clinical utility of 68Ga-MY6349 PET/CT imaging for detecting recurrent and metastatic thyroid cancer, and the results were compared with 68Ga-FAPI 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 68Ga-FAPI PET/CT, 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 68Ga-MY6349 and 68Ga-FAPI PET/CT 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

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