1. For patients with sTg <10 ng/ml due to discontinuation of L-T4 or sTg <5 ng/ml due to rhTSH application, TSH suppression therapy should be continued and closely followed, but empirical treatment with 131I is possible if there is a progressive increase in serum Tg or other evidence of disease progression (PD).
2. For patients with sTg >10ng/ml due to discontinuation of L-T4 or sTg >5ng/ml due to application of rhTSH, with persistently elevated Tg or TgAb levels and negative neck and chest imaging, 18F-FDG PET-CT, empirical 131I treatment at a dose of 100-200mCi is feasible. but if Rx-WBS is still negative, then If the Rx-WBS remains negative, however, the patient is classified as having iodine-refractory DTC and 131I therapy needs to be discontinued.