The influence of thyroglobulin on functional imaging in differentiated thyroid cancer.
OBJECTIVE
Recombinant human thyroid stimulating hormone (rhTSH) for an exogenous stimulation of TSH and consequent thyroglobulin (hTG) synthesis has reinitiated a discussion about the usefulness of diagnostic procedures for the follow-up of differentiated thyroid cancer (DTC).


METHODS
Fifty consecutive patients with DTC who received whole-body iodine scintigraphy (WBS) and positron emission tomography (PET) were evaluated.


RESULTS
The work-up was normal in 18/50. In 32 patients, functional imaging detected DTC. In 44% exogenous TSH stimulation with rhTSH was used and thyroxin was withdrawn in the others. The hTG under stimulation ranged from 0.8 to 5.004 ng x ml(-1). It was below 2 ng x ml(-1) in four (12.5%) patients. In total, 91 tumour sites were identified by positron emission tomography (PET) and 47 sites by WBS. PET and WBS showed corresponding uptake in 38% of lymph node, 48% of parenchymal and 43% of bone metastases. PET detected additional 53% of lymph node (WBS 9%), 38% of parenchymal (WBS 14%) and 28.5% of bone metastases.


CONCLUSIONS
It is concluded that PET is more sensitive than WBS for the detection of DTC. The follow-up of DTC patients with hTG levels alone misses a significant number of true positive cases. Its use should therefore be restricted to selected low risk patients only.
Menzel
C
C
Department of Nuclear Medicine, Hospital of the Johann W. Goethe University, Frankfurt, Germany. christian.menzel@em.uni-frankfurt.de
Zaplatnikov
K
K
Diehl
M
M
Döbert
N
N
Hamscho
N
N
Grünwald
F
F
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007457:Iodine Radioisotopes; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013954:Thyroglobulin / Q000097:blood*; D013964:Thyroid Neoplasms / Q000097:blood* / Q000000981:diagnostic imaging*; D013972:Thyrotropin; D014055:Tomography, Emission-Computed / Q000379:methods*; D014915:Whole-Body Counting / Q000379:methods*
D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; D013972:Thyrotropin; D013954:Thyroglobulin