title: Thyroid remnant ablation in patients with papillary cancer: a comparison of low, moderate, and high activities of radioiodine.
abstract: OBJECTIVE
  The consensus about optimal activities of I-131 for thyroid remnant ablation has not yet been achieved. The aim of this study was to compare ablation rates obtained with different I-131 activities.
  
  
  METHODS
  The study included 466 patients divided into four groups according to I-131 activities given after total thyroidectomy for papillary thyroid cancer: group A [168 patients who received 888 MBq (24 mCi)], group B [125 patients who received 1480 MBq (40 mCi)], group C [65 patients who received 1850 MBq (50 mCi)], and group D [108 patients who received 4440 MBq (120 mCi)]. Ablation outcome was assessed by whole-body scan in hypothyroid state 6-9 months after ablation and finally 18-21 months after the treatment.
  
  
  RESULTS
  The rate of successful ablation was similar in the group of patients who received 24 and 40 mCi (75 and 71.2%, respectively). The higher rate of ablation was achieved in the groups treated with 50 and 120 mCi of radioiodine (87.69 and 90.74%, respectively). The ablation rates at the first follow-up examinations (59.5, 67.2, 73.9, 80.6%) were lower than at second control study (75.0, 71.2, 87.7, 90.7%) in all groups. Time required for thyroid remnant ablation seems to be >or=18 months.
  
  
  CONCLUSIONS
  Our study indicates that activity of 50 mCi seems to be optimal to achieve a successful ablation rate (approximately 90%). Low I-131 activities are acceptable for lower risk patients because of satisfactory ablation rate (>70%), lower expense, and minimal radiation burden to patients as well as lower radiation exposure to clinical staff. The ablative use of high activities seems neither justified nor optimized.
authors.affiliation: Clinical Department of Nuclear Medicine and Radiation Protection, Clinical Hospital Centre Zagreb, Zagreb, Croatia. sanja.kusacickuna@gmail.com
authors.forename: Sanja
authors.initials: S
authors.lastname: Kusacic Kuna
authors.forename: Tatjana
authors.initials: T
authors.lastname: Samardzic
authors.forename: Vanja
authors.initials: V
authors.lastname: Tesic
authors.forename: Mario
authors.initials: M
authors.lastname: Medvedec
authors.forename: Krunoslav
authors.initials: K
authors.lastname: Kuna
authors.forename: Irena
authors.initials: I
authors.lastname: Bracic
authors.forename: Marija
authors.initials: M
authors.lastname: Despot
authors.forename: Damir
authors.initials: D
authors.lastname: Dodig
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002291:Carcinoma, Papillary / Q000000981:diagnostic imaging / Q000532:radiotherapy* / Q000601:surgery*; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000627:therapeutic use; D013961:Thyroid Gland / Q000000981:diagnostic imaging / Q000601:surgery*; D013964:Thyroid Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy* / Q000601:surgery*; D013965:Thyroidectomy; D013972:Thyrotropin / Q000097:blood; D016896:Treatment Outcome; D051598:Whole Body Imaging; D055815:Young Adult
chemical_list: D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals; D013972:Thyrotropin