Low-activity (2.0 GBq; 54 mCi) radioiodine post-surgical remnant ablation in thyroid cancer: comparison between hormone withdrawal and use of rhTSH in low-risk patients.
OBJECTIVE
(a) To compare the efficacy of low-activity (2 GBq; 54 mCi) (131)I ablation using l-thyroxine withdrawal or rhTSH stimulation, and (b) to assess the influence of thyroid remnants volume on the ablation rate.


METHODS
Patients underwent neck ultrasound, (131)I neck scintigraphy and radioiodine uptake. Post-therapy whole body scan (WBS) was acquired after 4-6 days. Ablation was assessed after 6-12 months by WBS, Tg and TgAb following l-thyroxine withdrawal.


METHODS
Group A: preparation by L-T(4) withdrawal (37 days); 21 patients received (131)I (2.02+/-0.22 GBq; 54.6+/-5.9 mCi) and on the day of treatment, TSH, Tg, TgAb were measured; Group B: stimulation by rhTSH; 21 patients received (131)I (1.97+/-0.18 GBq; 53.2+/-4.9 mCi) 24 h after the second injection of rhTSH (0.9 mg) and TSH, Tg and TgAb were measured after 2 days.


RESULTS
At follow-up, 90.0% of patients from group A and 85.0% of patients from group B had Tg levels <1 ng/ml; no uptake was observed in 95.2% and in 90.5% of patients from group A or B respectively, with no statistical differences for both ablation criteria. Before (131)I treatment, small thyroid remnants (<1 ml) were detected by US in <25% of all patients.


CONCLUSIONS
The use of rhTSH for the preparation of low-risk patients to ablation therapy with low activities of (131)I (2 GBq; 54 mCi) is safe and effective and avoids hypothyroidism. The presence of thyroid remnants smaller than 1 ml at US evaluation had no effect on the ablation rate.
Chianelli
M
M
Nuclear Medicine Unit, Department of Diagnostics, Regina Apostolorum Hospital, Albano, Rome, Italy. marcochianelli@libero.it
Todino
V
V
Graziano
F M
FM
Panunzi
C
C
Pace
D
D
Guglielmi
R
R
Signore
A
A
Papini
E
E
D000328:Adult; D000368:Aged; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007037:Hypothyroidism / Q000188:drug therapy / Q000453:epidemiology / Q000532:radiotherapy; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000188:drug therapy* / Q000453:epidemiology / Q000532:radiotherapy*; D011183:Postoperative Complications / Q000188:drug therapy / Q000453:epidemiology / Q000532:radiotherapy; D011877:Radionuclide Imaging; D011994:Recombinant Proteins / Q000627:therapeutic use; D012307:Risk Factors; D013964:Thyroid Neoplasms / Q000000981:diagnostic imaging / Q000453:epidemiology / Q000601:surgery*; D013972:Thyrotropin / Q000097:blood / Q000627:therapeutic use*; D013974:Thyroxine / Q000627:therapeutic use; D016896:Treatment Outcome; D055815:Young Adult
D007457:Iodine Radioisotopes; D011994:Recombinant Proteins; D013972:Thyrotropin; D013974:Thyroxine