Which thyroid cancer patients need periodic stimulation tests?
OBJECTIVE
Recurrences are frequent in thyroid cancer patients and long-term follow-up is therefore necessary. We evaluated the yield of rhTSH stimulation in three groups of patients, classified according to the UICC/TNM risk stratification and the results of first follow-up testing.


METHODS
The study population comprised 129 patients referred for rhTSH testing. All had undergone first follow-up testing after thyroid hormone withdrawal (off-T4) within 1 year of 131I ablation. Negative first follow-up testing was defined as Tg <2 ng/ml and no neck uptake on 131I diagnostic whole-body scan. Seventy-five patients had stage I thyroid cancer and negative first follow-up testing (group A), 19 had stage I disease and positive first follow-up testing (group B), and 35 had stage II-IV disease (group C). RhTSH stimulation was performed an average of 6 years after first follow-up testing.


RESULTS
131I diagnostic scanning after rhTSH was negative in all 75 group A patients. Only one group A patient had detectable Tg after rhTSH injection (1.5 ng/ml), but Tg had also been detected at baseline in this patient (1.45 ng/ml). Given the absence of a response to stimulation, suggesting an interference, Tg was reassessed with a different technique and proved to be undetectable (<0.1 ng/ml). Stimulation with rhTSH in group B showed residual Tg in seven patients and residual 131I uptake in the thyroid bed in two patients, but none of these patients had signs of disease progression. Five group C patients (14%) had a positive rhTSH test result, and this was suggestive of disease progression in at least two cases.


CONCLUSIONS
The first follow-up testing is essential for prognostic classification after 131I ablation of thyroid cancer. In stage I patients, undetectable Tg and negative 131I scan 1 year after ablation define a large population of subjects who have a very low risk of recurrence and who do not require further stimulation tests. In contrast, periodic rhTSH stimulation tests appear useful in higher-risk patients.
Zanotti-Fregonara
Paolo
P
Service de Médecine Nucléaire, Hôpital Saint-Antoine, 184, rue du Faubourg Saint-Antoine, 75571, Paris cedex 12, France.
Khoury
Alexandre
A
Duron
Françoise
F
Keller
Isabelle
I
Christin-Maître
Sophie
S
Kiffel
Thierry
T
Toubert
Marie Elisabeth
ME
Devaux
Jean-Yves
JY
Hindié
Elif
E
D000293:Adolescent; D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000000981:diagnostic imaging* / Q000517:prevention & control*; D018579:Patient Selection; D011379:Prognosis; D011877:Radionuclide Imaging; D018570:Risk Assessment / Q000379:methods; D013964:Thyroid Neoplasms / Q000000981:diagnostic imaging* / Q000628:therapy*; D013965:Thyroidectomy; D013972:Thyrotropin; D016896:Treatment Outcome
D007457:Iodine Radioisotopes; D013972:Thyrotropin