F-18 FDG-PET/CT evaluation of patients with differentiated thyroid cancer with negative I-131 total body scan and high thyroglobulin level.
OBJECTIVE
The aim was to evaluate the incremental diagnostic rate of F-18 fluoro-fluorodeoxygulose positron emission tomography/computed tomography (F-18 FDG-PET/CT) in patients with negative I-131 whole body scans and high Tg levels. The secondary end points were correlations between F-18 FDG-PET/CT positive results and Tg levels and comparison between F-18 FDG-PET/CT accuracy in patients "on-therapy" with suppressed thyroid stimulating hormone (TSH) and those with high TSH levels.


METHODS
We studied 52 patients who had undergone total thyroidectomy and remnant ablation; they had high Tg levels (average = 156 ng/mL; SD +/- 274) after 3 weeks of levothyroxine withdrawal and negative I-131 total body scans after therapeutic doses.


RESULTS
We noted a statistically significant positive correlation between F-18 FDG-PET/CT positive results and Tg levels, irrespective of levothyroxine therapy regimen. Tg levels between F-18 FDG-PET/CT positive/negative groups were significantly different and we did not note any statistically significant correlation between F-18 FDG-PET/CT results and TSH levels, tumor size, and combination of Tg/TSH levels.


CONCLUSIONS
Our results indicate that F-18 FDG-PET/CT is a useful diagnostic tool in patients with differentiated thyroid carcinoma and with negative I-131 total body scans and high Tg levels. The levothyroxine therapy regimen does not influence F-18 FDG-PET/CT results and the rate of F-18 FDG-PET/CT positive results appears to correlate with the Tg levels. The highest accuracy is reached when the study is performed for patients with Tg levels higher than 21 ng/mL.
Bertagna
Francesco
F
Department of Nuclear Medicine, Spedali Civili Brescia, Brescia, Italy. francesco.bertagna@spedalicivili.brescia.it
Bosio
Giovanni
G
Biasiotto
Giorgio
G
Rodella
Carlo
C
Puta
Erinda
E
Gabanelli
Sara
S
Lucchini
Silvia
S
Merli
Giuseppe
G
Savelli
Giordano
G
Giubbini
Raffaele
R
Rosenbaum
Joshua
J
Alavi
Abass
A
D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007457:Iodine Radioisotopes; D008297:Male; D049268:Positron-Emission Tomography; D012372:ROC Curve; D012680:Sensitivity and Specificity; D013954:Thyroglobulin / Q000097:blood*; D013964:Thyroid Neoplasms / Q000097:blood* / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed; D051598:Whole Body Imaging
D007457:Iodine Radioisotopes; D019788:Fluorodeoxyglucose F18; D013954:Thyroglobulin