Abstract
The analysis of serum thyroglobulin (Tg) following thyroid-stimulating hormone (TSH) stimulation (sTg) has been recommended in the follow-up of differentiated thyroid carcinoma (DTC) patients, however, its routine use remains controversial. The aim of the current study was to evaluate the accuracy of sTg testing following recombinant human (rh) TSH stimulation in DTC patients, with a follow-up of 12.4 years. Retrospective studies were conducted of 125 DTC patients, who underwent rhTSH stimulation testing between 1999 and 2002. The exclusion criteria were: Patients with anti-Tg antibodies, Tg levels >1 ng/ml under TSH suppression and the absence of radioactive iodine (RAI) ablation therapy following surgery. In total, 49 patients were included in the study and all had been previously treated with total or near total thyroidectomy (with or without central neck dissection) and RAI, postoperatively. The Tg functional sensitivity was 1.0 ng/ml. The follow-up for patients was performed annually. During the median follow-up of 12.4 years after the rhTSH stimulation test, nine patients exhibited recurrence (18.4%). Of the nine patients, six exhibited sTg levels >2 ng/ml (positive result) and three exhibited levels <2 ng/ml (negative result). Relapse occurred at a mean of 5.9 years following the rhTSH stimulation test. The positive predictive value and negative predictive value (NPV) of positive sTg were 50 and 91.9%, respectively, with a sensitivity of 66.6% and a specificity of 85.0%. The rhTSH-stimulated Tg levels have a high NPV, allowing the identification of the patients who are free of the tumour. These results are consistent with the previously published data; however, to the best of our knowledge, this is the study with the longest follow-up duration after rhTSH stimulation.
Highlights
Thyroid carcinoma comprises 1‐2% of all malignancies in the USA [1]
As the majority of the studies published far have a short‐term follow‐up after the rhTSH stimulation test (≤7 years), and recurrence may occur in up to one‐third of cases after the first decade, the present study aimed to evaluate the accuracy of rhTSH‐stimulated Tg levels in patients with undetectable supTg values, to predict the remission after a follow‐up of 12.4 years
Distant metastases were observed in one patient when the initial cancer diagnosis was determined; an excellent response to therapy was exhibited, resulting in negative 131I WBS and serum supTg levels
Summary
Thyroid carcinoma comprises 1‐2% of all malignancies in the USA [1]. Epidemiological studies have shown an increasing prevalence of differentiated thyroid carcinoma (DTC); the mortality rate has remained stable, most likely due to the increased diagnostic scrutiny [2]. According to the American Thyroid Association recommendations [7], the disease‐free status comprises all of the following: i) No clinical evidence of tumour; ii) no imaging evidence of tumour [i.e. no uptake outside the thyroid bed on the initial post‐treatment whole‐body scan (WBS) or, if uptake outside the thyroid bed is present, no imaging evidence of tumour on a recent diagnostic scan and neck ultrasound (US) is observed]; and iii) undetectable serum thyroglobulin (Tg) levels during thyroid‐stimulating hormone (TSH) suppression and stimulation in the absence of interfering antibodies
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