Utility of repeated recombinant human TSH (rhTSH)-stimulated tiroglobulin (Tg) test in patients with differentiated thyroid carcinoma (DTC) without evidence of disease at their initial rh-TSH-stimulation test
A. Oleaga, F. Goñi, M. Paja, A. Izuzquiza, C. Moreno, V. Arosa, N. Iglesias & J. Espiga
Current guidelines recommend measurement of rhTSH-stimulated Tg, with neck ultrasound 612 months after the initial therapy for DTC (Total thyroidectomy plus 100 mCiI131 ablation of the thyroid bed). Uncertainty persists regarding whether the subsequent follow up should be based on measurement of basal serum Tg or whether rhTSH-stimulated Tg should be performed and at what frequency. The aim of our study was to evaluate the utility of repeated rhTSH-stimulated Tg.
This was a retrospective study of 40 patients; 30 female; mean age was 45.5 years (2574); Histology: 32 Papillary, (3 follicular variant and 1 tall cell variant); 7 Follicular. Initial disease stage I n=28; II, n=3; III, n=7; IV, n=2. Mean tumor size was 2.61 cm. Pre-I131 ablation Tg levels were 7.4 ng/mL (029.2)(functional sensitivity 0.9 ng/mL). All of them had an undetectable rhTSH-stimulated Tg with undetectable Tg antibodies at initial evaluation. The number of repeated tests performed varied from 1 to 3 during a follow-up period of 48132 months. (1 in n=40; 2 in n=34; 3 in n=12).
Tg was undetectable in all patients in the first test. In three patients Tg become detectable in the second or third: 1 patient false positive, 1 patient showed supraclavicular nodal disease (basal Tg was also detectable) and other developed lung metastases. Both patients were older than 65 years old and had at the time of diagnosis a stage III disease with extrathyroidal extension of the tumor and unfavorable histology (columnar cell).
In our patients with DTC, the first rhTSH-stimulated Tg is an excellent predictor of remission independent of clinical stage at presentation. In our experience repeated rhTSH stimulating testing was of limited value although a second negative test performed 5 years after initial treatment might assure clinical remission. Most of the patients can be followed up with basal Tg and neck ultrasound.
Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.
Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector