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The Quarterly Journal of Nuclear Medicine and Molecular Imaging 2019 Mar 25

DOI: 10.23736/S1824-4785.19.03136-4

Copyright © 2019 EDIZIONI MINERVA MEDICA

language: English

Prognostic value and optimal threshold of first thyroglobulin in low/intermediate risk DTC

Seyed R. ZAKAVI 1, Narjess AYATI 1, Samira ZARE 1, Abolfazl AYATI 1, Kayvan SADRI 1, Nazanin FEKRI 2, Bita ABBASI 3, Susan SHAFIEI 1

1 Nuclear Medicine Research Center, Mashhad University of Medical Sciences, Mashhad, Iran; 2 Department of Statistics, Mashhad University of Medical Sciences, Mashhad, Iran; 3 Department of Radiology, Mashhad University of Medical Sciences, Mashhad, Iran



BACKGROUND: The aim of this study was to define prognostic value and optimal threshold of first thyroglobulin (fTg) measured after thyroidectomy and just before radio-iodine therapy (RIT), in low/intermediate risk patients with differentiated thyroid cancer (DTC).
MATERIALS: This is a retrospective study in 383 patients with DTC who were treated with surgery followed by RIT. Response to treatment was assessed 1 and 2 years after RIT. Odds ratio of different risk factors like age, sex, TNM stage, fTg and Anti-Tg Ab were compared between patients with and without incomplete response 1 and 2 years after treatment. Receiver operating curve analysis was used for definition of optimal fTg cut off for detection of incomplete response.
RESULTS: 218 female and 55 male with DTC had negative anti-Tg antibody (mean age: 37.5±14.5 years) and analyzed separately. fTg≥33.5 ng/ml and fTg/TSH ratio of ≥0.36 had the optimal sensitivity and specificity for detection of incomplete response 1 and 2 years after treatment. fTg<35ng/ml had NPV of 98.5% for exclusion of distant metastases. Patients with fTg≥33.5ng/ml had longer “time to excellent response” (3.6±2.3 vs 2.0±1.8 yrs) and needed more additional treatments compared to patients with fTg<35 ng/ml. Multivariate analysis showed that fTg was the most potent risk factor for prediction of treatment failure 1 and 2 years after RIT.
CONCLUSIONS: fTg of ≥35.5 ng/ml was the most important risk factor for prediction of treatment failure after RIT and could be included in decision algorithms regarding intensity of treatments in low/intermediate risk patients with DTC.


KEY WORDS: Differentiated thyroid cancer - Prognosis - Thyroglobulin - Iodine therapy

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