Superior Diagnostic Performance of ⁶⁸Ga-FAPI PET/CT Compared With ⁶⁸Ga-DOTATATE PET/CT in Medullary Thyroid Carcinoma.

A 60-year-old woman with synchronous papillary and medullary thyroid carcinomas (MTC) underwent total thyroidectomy and adjuvant therapy. In later course of her MTC disease, an elevation of serum calcitonin prompted 68 Ga-DOTATATE imaging, revealing mildly avid loco-regional and osseous metastases as well as non-avid nodal and hepatic metastases. 68 Ga-FAPI PET/CT demonstrated superior detection compared with 68 Ga-DOTATATE PET/CT, particularly in hepatic lesions. 177 Lu-FAPI-2286 radioligand therapy (RLT) was administered but failed to achieve biochemical response, though it was well tolerated. This case highlights the diagnostic advantage of FAP-targeted imaging in advanced MTC and underscores the need for standardized RLT protocols and exploration of combination therapeutic strategies.