The role of F-18-fluorodeoxyglucose positron emission tomography in the postoperative evaluation of differentiated thyroid cancer.
OBJECTIVE
The objective of the study was to compare F-18-fluorodeoxyglucose position emission tomography (FDG-PET) with diagnostic whole body scanning (DxWBS) and post-ablation radioiodine whole body scanning (TxWBS) and to assess its prognostic value in newly diagnosed differentiated thyroid cancer (DTC) patients, hypothesizing that FDG-PET is more likely to disclose locoregional and distant metastases.


METHODS
DxWBS and FDG-PET scanning were performed in 26 newly diagnosed DTC patients who underwent thyroidectomy and TxWBS in 24 cases who had radioactive iodine ablation. The results of the FDG-PET scans were correlated with the stage of the disease and the long-term outcome of DTC.


RESULTS
Overall, 18 FDG-PET scans (69.2%) were positive showing a total of 40 foci while 8 scans (30.8%) were negative. The corresponding 26 DxWBS were all positive and showed a total of 47 foci. DxWBS and TxWBS showed similar foci in the 24 patients who had ablation therapy. In contrast to the FDG-PET scans that showed uptake of 26 foci (65%) outside the thyroid bed, 45 foci (95.7%) on DxWBS were in the thyroid bed while 2 foci (4.3%) were in cervical lymph nodes and no focus was seen outside the neck area (P=0.000). There was a clear correlation between the FDG-PET results, the stage of the disease and long-term outcome; seven of the eight negative FDG-PET scans were in stage 1, while all patients with disease higher than stage 1 (six patients) had positive scans. Over a median of 30 months (10-48), seven out of eight patients (87.5%) with negative FDG-PET scans were in remission compared with only eight patients (44.4%) with positive FDG-PET (P=0.04).


CONCLUSIONS
In the postoperative evaluation of DTC, compared with DxWBS and TxWBS, FDG-PET scans are more likely to reveal uptake outside the thyroid bed and to correlate with the stage of the disease and long-term outcome.
Alzahrani
Ali S
AS
Department of Medicine (MBC-46), King Faisal Specialist Hospital and Research Centre, PO Box 3354, Riyadh 11211, Saudi Arabia. aliz@kfshrc.edu.sa
Al-Zahrani
Ali S
AS
Abouzied
Mohei-Eldin M
ME
Salam
Suzan Abdel
SA
Mohamed
Gamal
G
Rifai
Ayman
A
Al Sugair
Abdulaziz
A
Amin
Tarik
T
D000293:Adolescent; D000328:Adult; D000368:Aged; D002454:Cell Differentiation; D005260:Female; D019788:Fluorodeoxyglucose F18; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009333:Neck / Q000000981:diagnostic imaging; D049268:Positron-Emission Tomography / Q000379:methods*; D011184:Postoperative Period; D011379:Prognosis; D019275:Radiopharmaceuticals; D013964:Thyroid Neoplasms / Q000000981:diagnostic imaging* / Q000601:surgery; D051598:Whole Body Imaging
D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18