First-in-Human Experience With 177Lu-DOTAGA.(SA.FAPi)2 Therapy in an Uncommon Case of Aggressive Medullary Thyroid Carcinoma Clinically Mimicking as Anaplastic Thyroid Cancer

Abstract A 56-year-old man was diagnosed with calcitonin negative, plasma chromogranin A–positive, immunohistochemistry-negative, high-grade MTC (medullary thyroid cancer) behaving clinically like anaplastic thyroid cancer and presented with progressive disease after conventional therapies. A theranostic approach of 68 Ga-DOTA.SA.FAPi–guided 177 Lu-DOTAGA.(SA.FAPi) 2 radionuclide therapy was administered on compassionate grounds as per the Declaration of Helsinki because known standard lines of treatment were ineffective. Treatment with a single cycle of 1.65 GBq 177 Lu-DOTAGA.(SA.FAPi) 2 demonstrated a sustainable reduction in the neck mass with significant improvement in the quality of life of the patient. 177 Lu-DOTAGA.(SA.FAPi) 2 is a potential theranostic option for high-grade MTC refractory to standard therapeutic options.