TG and neoplasm: No risks were found among age, gender, capsular invasion, TNM stage and time interval between surgery and 131I. In contrast, tumor stage T3 or T4, LN metastasis to lateral cervical region (N1b) station, intermediate and high risks, pre-ablation Tg ≥ 3.525 ng/ml and TSH < 99.700 μIU/mL were significantly associated with a therapeutic failure (Table 3).