ORIGINAL ARTICLE   

The Quarterly Journal of Nuclear Medicine and Molecular Imaging 2021 March;65(1):64-71

DOI: 10.23736/S1824-4785.19.03136-4

Copyright © 2019 EDIZIONI MINERVA MEDICA

lingua: Inglese

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

S. Rasoul 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).
METHODS: 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<33.5 ng/mL had NPV of 98.5% for exclusion of distant metastases. Patients with fTg≥33.5 ng/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<33.5 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 ≥33.5 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: Thyroid neoplasms; Prognosis; Thyroglobulin; Iodine