Thyroid remnant ablation in patients with papillary cancer: a comparison of low, moderate, and high activities of radioiodine.
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.
Kusacic Kuna
Sanja
S
Clinical Department of Nuclear Medicine and Radiation Protection, Clinical Hospital Centre Zagreb, Zagreb, Croatia. sanja.kusacickuna@gmail.com
Samardzic
Tatjana
T
Tesic
Vanja
V
Medvedec
Mario
M
Kuna
Krunoslav
K
Bracic
Irena
I
Despot
Marija
M
Dodig
Damir
D
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
D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals; D013972:Thyrotropin