Monitoring differentiated thyroid cancer patients with negative serum thyroglobulin

Summary

Aim: Serum antithyroglobulin antibody (TgAb) has been reported as a surrogate marker for differentiated thyroid cancer (DTC) in some conditions. We investigated changes in serum TgAb levels after stimulation with thyroid- stimulating hormone (TSH) and the clinical implications for monitoring DTC. Patients, methods: We retrospectively enrolled 53 DTC patients who had undergone total thyroidectomy and were negative for serum Tg and positive for TgAb. Patients underwent highdose radioactive iodine treatment, and serum TgAb was measured before (TgAb_BAS) and after TSH stimulation (TgAb_STIM). TgAb was followed up 6 to 12 months later (TgAb_F/U). The change in TgAb after TSH stimulation ΔTgAb- _STIM) was calculated as a percentage of the baseline level. Patient disease status was classified into no residual disease (ND) and residual or recurred disease (RD) by follow-up imaging studies and pathologic data. The characteristics and diagnostic value of serum TgAb levels and ΔTgAb_ST|_M were investigated with respect to disease status. Results: 38 patients were in the ND group and 15 were in the RD group. TgAb_BAS, TgAb_STIM and TgAb_F/U were significantly higher in the RD compared to the ND group (p = 0.0008, 0.0002, and < 0.0001, respectively). ΔTgAb_STIM was also significantly higher in the RD group (p = 0.0009). In the patients who presented with obviously high (> 50%) or low (< -50%) ΔTgAb_STIM, the proportions in the RD group were markedly different at 100% and 7%, respectively. ΔTgAb_STIM had significant diagnostic value for RD (p < 0.001). Conclusion: The change in serum TgAb level after TSH stimulation is different between the RD and ND groups, and thus, it may be used as a surrogate diagnostic marker for DTC when the serum Tg is negative and TgAb is positive.

Zusammenfassung

Ziel: Serumantikörper gegen Thyreoglobulin (Tg-AK) gelten unter bestimmten Bedingungen als Surrogatmarker für das differenzierte Schilddrüsenkarzinom (DTC). Wir untersuchten Veränderungen der Tg-AK-Spiegel im Serum nach Stimulation mit Thyreoglobulin (TSH) und die klinischen Folgen für die DTC- Überwachung. Patienten, Methoden: Wir rekrutierten retrospektiv 53 DTC-Patienten nach kompletter Thyreoidektomie, die ein negatives Serum-Tg aufwiesen und positiv für Tg-AK waren. Die Patienten erhielten eine hochdosierte Radiojodtherapie; Serum-Tg-AK wurden vor (Tg-AK_BAS) sowie nach TSH-Sti- mulation (Tg-AK_STIM) bestimmt. Die Tg-AK wurden danach 6 bis 12 Monate lang kontrolliert (Tg-AK_FU). Die Änderung bei Tg-AK nach TSH-Stimulation ^Tg-AK_STIM) wurde als Prozentwert des Baseline-Spiegels berechnet. Die Patienten wurden anhand von Kontrollaufnahmen und krankheitsbezogenen Daten einem Krankheitsstadium ohne Residualtumor (ND) bzw. mit Residualtumor oder Rezidivtumor (RD) zugeordnet. Merkmale und diagnostischer Wert von Tg-AK-Spiegeln und ΔTg-AK_STIM wurden in Bezug auf das Krankheitsstadium untersucht. Ergebnisse: In der ND-Gruppe waren 38 Patienten und 15 in der RD-Gruppe. Tg-AK_BAS, Tg-AK_STIM und Tg- AK_F/U waren in der RD-Gruppe signifikant höher als in der ND-Gruppe (p = 0,0008, 0,0002 bzw. < 0,0001). ΔTg-AK_STIM war in der RD- Gruppe ebenfalls signifikant höher (p = 0,0009). In der RD-Gruppe waren die Patienten mit sichtlich hohen (> 50%) oder niedri- gen (< 50%) ΔTg-AK_STIM-Werten mit 100% vs. 7% anteilig sehr unterschiedlich vertreten. Für die RD-Gruppe hatte ΔTg-AK_STIM einen bedeutsamen diagnostischen Wert. Schlussfolgerung: Die RD- und ND-Gruppe unterschieden sich hinsichtlich der Veränderung des Serum-Tg-AK-Spiegels nach TSH- Stimulation. Somit ist es möglich, diese als diagnostischen Surrogatmarker für DTC zu nutzen, wenn das Serum-Tg negativ und Tg- AK positiv sind.

Keywords

Differentiated thyroid cancer - thyroglobulin - antithyroglobulin antibody - thyroid-stimulating hormone

Schlüsselwörter

Differenziertes Schilddrüsenkarzinom - Thyreoglobulin-Antikörper - Thyrotropin

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