177Lu-CTR-FAPI for the Treatment of Thyroid Cancer

Inclusion Criteria: * Histologically confirmed diagnosis of thyroid cancer according to the 2022 WHO classification of thyroid tumors. Differentiated thyroid carcinoma must be diagnosed as radioactive iodine-refractory (RAIR) by a nuclear medicine specialist. * Evidence of progressive disease based on RECIST 1.1 criteria in pre-treatment imaging. * Prior surgical resection of resectable cervical lesions, with currently unresectable systemic disease. * Previous targeted therapy was discontinued due to intolerance, or lack of benefit from targeted therapy assessed by investigator, or patient refusal. * At least one measurable target metastatic lesion on contrast-enhanced CT/MRI (longest diameter of lesion ≥ 10 mm or shortest diameter of lymph node ≥ 15 mm). * Positive CTR-FAPI uptake in lesions, defined as SUVmax \> 10 in more than half of the lesions on 68Ga-CTR-FAPI PET/CT. * Life expectancy \> 6 months. * ECOG performance status ≤ 2. * Prior anti-tumor therapy-related toxicities that recoverd to Grade 0 or 1 (except alopecia, pigmentation, or chronic radiation toxicities and deemed irreversible by the investigator). * For subjects with fertility: agreement to use effective contraception during treatment and 4 months (males) or 7 months (females) after the last dose. * Voluntary participation and signed informed consent. Exclusion Criteria: * Presence of CTR-FAPI-negative lesions (i.e., malignant lesions on contrast-enhanced CT/MRI without uptake on 68Ga-CTR-FAPI PET/CT). * Prior therapeutic radionuclide therapy (except 131I). * Systemic anti-cancer therapy (including chemotherapy, targeted therapy, immunotherapy, radionuclide therapy, or anti-tumor traditional Chinese medicine) within 4 weeks before the first dose. * Participation in another drug or device clinical trial within 4 weeks before the first dose. * Insufficient major organ function. * Severe or uncontrolled comorbidities. * Presence of pleural effusion or ascites requiring intervention or judged uncontrolled by the investigator at screening. * Active infection within 4 weeks before the first dose. * Women who are pregnant, breastfeeding, or planning pregnancy. * Known allergy to contrast agents. * History of symptomatic central nervous system metastases. * Other concurrent malignancies. * Surgery under general anesthesia within 8 weeks before the first dose. * History of acute coronary syndrome or stroke within 8 weeks before the first dose. * Severe claustrophobia. * Any other condition deemed inappropriate for participation by the investigator (e.g., poor compliance, inability to cooperate with treatment and follow-up).