First proof-of-concept [68Ga]Ga-DOTA-CCK-66 PET/CT imaging in patients suffering from metastatic MTC revealed high tracer accumulation in lesions and no significant uptake in healthy organs except in the stomach (endogenously expressing CCK-2R) and the kidneys (tracer excretion). The gene discussed is CCKBR; the disease is medullary thyroid gland carcinoma.