Basal serum thyroglobulin measured by a second-generation assay is equivalent to stimulated thyroglobulin in identifying metastases in patients with differentiated thyroid cancer with low or intermediate risk of recurrence.
BACKGROUND
Guidelines for the follow-up of differentiated thyroid cancer (DTC) recommend the measurement of TSH-stimulated thyroglobulin (s-Tg) instead of basal Tg on T4 therapy (b-Tg). However, these guidelines were established using first-generation Tg assays with a functional sensitivity (FS) of 0.5-1.0 ng/ml. Current more sensitive second-generation Tg assays (Tg2G; FS 0.05-0.10 ng/ml) have shown that low-risk DTC patients with undetectable b-Tg rarely have recurrences.


OBJECTIVE
This study was undertaken to compare b-Tg using a chemiluminescent Tg2G assay (Tg2GICMA; FS 0.1 ng/ml) with s-Tg in DTC patients with an intermediate risk of recurrence.


METHODS
We evaluated 168 DTC patients with a low (n = 101) and intermediate (n = 67) risk of recurrence treated by total thyroidectomy (147 also treated with radioiodine), with a mean follow-up of 5 years.


RESULTS
b-Tg was undetectable with the Tg2GICMA in 142 of 168 patients. s-Tg was <2 ng/ml in 138 of these 142 patients, and only 3 of these 138 (2%) presented metastases on cervical ultrasound (US). Of the 4 of 142 patients with s-Tg >2 ng/ml, 1 had cervical metastases seen after radioiodine. Furthermore, 26 of 168 patients presented detectable b-Tg with the Tg2GICMA; 17 of these 26 patients also presented s-Tg >2 ng/ml. In 10 of these 17 patients, metastases were detected. Cervical US or b-Tg were positive in 14 of 15 patients with recurrent disease. Globally, the sensitivity and negative predictive value of the Tg2GICMA plus US were 93 and 99%, respectively.


CONCLUSIONS
b-Tg measured with a Tg2GICMA and cervical US, used together, are equivalent to s-Tg in identifying metastases in patients with DTC with a low or intermediate risk of recurrence.
Laboratory of Molecular and Translational Endocrinology, Division of Endocrinology, Department of Medicine, Escola Paulista de Medicina, Universidade Federal de São Paulo, Brazil ; Thyroid Diseases Center, Instituto Israelita de Ensino e Pesquisa Albert Einstein, Brazil ; Fleury Medicina e Saúde, São Paulo, Brazil.
Cláudia C D
CC
Nakabashi
Laboratory of Molecular and Translational Endocrinology, Division of Endocrinology, Department of Medicine, Escola Paulista de Medicina, Universidade Federal de São Paulo, Brazil.
Teresa S
TS
Kasamatsu
Laboratory of Molecular and Translational Endocrinology, Division of Endocrinology, Department of Medicine, Escola Paulista de Medicina, Universidade Federal de São Paulo, Brazil.
Felipe
F
Crispim
Laboratory of Molecular and Translational Endocrinology, Division of Endocrinology, Department of Medicine, Escola Paulista de Medicina, Universidade Federal de São Paulo, Brazil.
Claudia A
CA
Yamazaki
Laboratory of Molecular and Translational Endocrinology, Division of Endocrinology, Department of Medicine, Escola Paulista de Medicina, Universidade Federal de São Paulo, Brazil ; Thyroid Diseases Center, Instituto Israelita de Ensino e Pesquisa Albert Einstein, Brazil.
Cléber P
CP
Camacho
Laboratory of Molecular and Translational Endocrinology, Division of Endocrinology, Department of Medicine, Escola Paulista de Medicina, Universidade Federal de São Paulo, Brazil ; Thyroid Diseases Center, Instituto Israelita de Ensino e Pesquisa Albert Einstein, Brazil.
Danielle M
DM
Andreoni
Laboratory of Molecular and Translational Endocrinology, Division of Endocrinology, Department of Medicine, Escola Paulista de Medicina, Universidade Federal de São Paulo, Brazil ; Thyroid Diseases Center, Instituto Israelita de Ensino e Pesquisa Albert Einstein, Brazil.
Rosalia P
RP
Padovani
Laboratory of Molecular and Translational Endocrinology, Division of Endocrinology, Department of Medicine, Escola Paulista de Medicina, Universidade Federal de São Paulo, Brazil ; Thyroid Diseases Center, Instituto Israelita de Ensino e Pesquisa Albert Einstein, Brazil.
Elza S
ES
Ikejiri
Laboratory of Molecular and Translational Endocrinology, Division of Endocrinology, Department of Medicine, Escola Paulista de Medicina, Universidade Federal de São Paulo, Brazil ; Thyroid Diseases Center, Instituto Israelita de Ensino e Pesquisa Albert Einstein, Brazil.
Maria C O M
MC
Mamone
Fleury Medicina e Saúde, São Paulo, Brazil.
Flávia C
FC
Aldighieri
Thyroid Diseases Center, Instituto Israelita de Ensino e Pesquisa Albert Einstein, Brazil.
Jairo
J
Wagner
Laboratory of Molecular and Translational Endocrinology, Division of Endocrinology, Department of Medicine, Escola Paulista de Medicina, Universidade Federal de São Paulo, Brazil ; Thyroid Diseases Center, Instituto Israelita de Ensino e Pesquisa Albert Einstein, Brazil.
Jairo T
JT
Hidal
Laboratory of Molecular and Translational Endocrinology, Division of Endocrinology, Department of Medicine, Escola Paulista de Medicina, Universidade Federal de São Paulo, Brazil ; Fleury Medicina e Saúde, São Paulo, Brazil.
José G H
JG
Vieira
Laboratory of Molecular and Translational Endocrinology, Division of Endocrinology, Department of Medicine, Escola Paulista de Medicina, Universidade Federal de São Paulo, Brazil ; Thyroid Diseases Center, Instituto Israelita de Ensino e Pesquisa Albert Einstein, Brazil ; Fleury Medicina e Saúde, São Paulo, Brazil.
Rosa P M
RP
Biscolla
Laboratory of Molecular and Translational Endocrinology, Division of Endocrinology, Department of Medicine, Escola Paulista de Medicina, Universidade Federal de São Paulo, Brazil ; Thyroid Diseases Center, Instituto Israelita de Ensino e Pesquisa Albert Einstein, Brazil ; Fleury Medicina e Saúde, São Paulo, Brazil.
Rui M B
RM
Maciel
Differentiated thyroid cancer; Highly sensitive thyroglobulin assay; TSH-stimulated thyroglobulin test; Thyroglobulin