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 68Ga-DOTATATE imaging, revealing mildly avid loco-regional and osseous metastases as well as non-avid nodal and hepatic metastases. 68Ga-FAPI PET/CT demonstrated superior detection compared with 68Ga-DOTATATE PET/CT, particularly in hepatic lesions. 177Lu-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.