Which thyroid cancer patients need periodic stimulation tests?

• Published in: European journal of nuclear medicine and molecular imaging Vol. 34; no. 4; pp. 541 - 546
• Main Authors: Zanotti-Fregonara, Paolo, Khoury, Alexandre, Duron, Françoise, Keller, Isabelle, Christin-Maître, Sophie, Kiffel, Thierry, Toubert, Marie Elisabeth, Devaux, Jean-Yves, Hindié, Elif
• Format: Journal Article
• Language: English
• Published: Germany Springer Nature B.V 01.04.2007
• Subjects: Adolescent; Adult; Aged; Diagnostics; Female; Humans; Iodine Radioisotopes - therapeutic use; Male; Medical imaging; Middle Aged; Neoplasm Recurrence, Local - diagnostic imaging; Neoplasm Recurrence, Local - prevention & control; Patient Selection; Prognosis; Radionuclide Imaging; Risk Assessment - methods; Thyroid cancer; Thyroid diseases; Thyroid Neoplasms - diagnostic imaging; Thyroid Neoplasms - therapy; Thyroidectomy; Thyrotropin; Treatment Outcome
• ISSN: 1619-7070; 1619-7089
• DOI: 10.1007/s00259-006-0279-z

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. 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. 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. 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.