title: Low-dose radioiodine ablation in differentiated thyroid cancer with macroscopic extrathyroidal extension and low level of preablative-stimulated thyroglobulin.
abstract: OBJECTIVE
  High-dose radioactive iodine (RAI) is recommended for patients with nonmetastatic differentiated thyroid cancer with macroscopic extrathyroidal extension (MAEE). It is unclear whether these patients can be treated with low-dose RAI when preablative-stimulated thyroglobulin (ps-Tg) is low. This randomized study aims to evaluate the clinical outcome and ablative efficacy of low-dose radioiodine in patients with MAEE but with low ps-Tg level.
  
  
  METHODS
  Differentiated thyroid cancer patients with complete thyroidal resection, MAEE, any N stage, ps-Tg less than or equal to 5 ng/ml when thyroglobulin antibodies are less than or equal to 46 IU/ml, and no evidence of distant metastasis were included in the study. Patients were randomly allocated to receive low-dose (1110 MBq) or high-dose RAI (3700 MBq). Follow-up was generally performed 6 months after ablation. Successful ablation was identified as (i) stimulated thyroglobulin 1.0 ng/ml or less when thyroglobulin antibodies 46 IU/ml or less; (ii) negative Dx-WBS; and (iii) negative neck ultrasonography. Clinical recurrence was defined as the reappearance of disease confirmed by cytology or pathology.
  
  
  RESULTS
  A total of 102 patients were analyzed: 51 in the low-dose group and 51 in the high-dose group. There was no significant difference in clinicopathological characters between the two groups. No patient had clinical recurrences during the mean 6.8 months of follow-up. Ablation was successful in 43 of 51 (84.3%) patients in the low-dose group and in 44 of 51 (86.27%) patients in the high-dose group, and thus no significant difference was noted (P=0.7798).
  
  
  CONCLUSIONS
  Ablation with low-dose RAI has been proven to be noninferior to high-dose RAI in nonmetastatic patients with MAEE when ps-Tg level is less than 5 ng/ml.
authors: aDepartment of Nuclear Medicine, Peking Union Medical College Hospital, Beijing bDepartment of Oncology, The Affiliated Hospital of Qingdao University, Qingdao, China.
authors: Yingjie
authors: Y
authors: Zhang
authors: Jun
authors: J
authors: Liang
authors: Xue
authors: X
authors: Yang
authors: Ke
authors: K
authors: Yang
authors: Yansong
authors: Y
authors: Lin
mesh_terms: D055011:Ablation Techniques; D000328:Adult; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D013954:Thyroglobulin / Q000378:metabolism*; D013964:Thyroid Neoplasms / Q000378:metabolism* / Q000473:pathology / Q000601:surgery*; D013972:Thyrotropin / Q000494:pharmacology; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D007457:Iodine Radioisotopes; D013972:Thyrotropin; D013954:Thyroglobulin