Fig. 1

Distribution of RR-DTC. 1. The foci never concentrate RAI; 2. Despite previous evidence of RAI concentration, the foci lose the ability to be RAI-avid; 3. Despite the significant concentration of RAI, concentration is presented in some foci but not in others; 4. Metastasis progression within 1 year after RAI therapy; 5. RAI doses of > 600 mCi. Patients who meet the characteristics of types 1–4 are defined as having the corresponding RR-DTC type, and those who do not meet the criteria of types 1–4 are defined as having RR-DTC type 5. RAI, radioactive iodine; RR-DTC, radioiodine refractory differentiated thyroid carcinoma