Influence of the thyroid remnant in the elevation of the serum thyroglobulin after thyroidectomy in differentiated thyroid carci

Abstract
Purpose  Stimulated thyroglobulin (Tg) and 131I total-body scan (TBS) have been the mainstays of differentiated thyroid carcinoma (DTC), but now diagnostic TBS has been
eliminated from some follow-up protocols. Nevertheless, Tg can be negative in the presence of thyroid tissue, and moderately
elevated Tg poses management problems. The purpose of this study was to check how many patients have Tg negative but visible
thyroid tissue and if diagnostic TBS could be clinically useful.

Material and methods  Retrospective review of 317 exams (stimulated Tg and TBS) of 128 patients with DTC. Patients with high-grade criteria and/or
positive autoantibodies are excluded. Tg is considered positive if higher than the sensitivity level of the technique. TBS
is positive if thyroid remnant, lymphatic node or metastases are detected. Results are classified in Tg and TBS concordant
or discordant.

Results  Discordant 131I TBS and Tg were found in 74/317 studies (23.3%), 48 (65%) being TBS positive and Tg negative. None of 128 patients had a
first post-surgery negative scan, but 13 (10%) were Tg negative, even two patients with lymph node uptake. One year after
radioiodine treatment, 26 out of 115 patients (initially Tg and TBS concordant positive) showed Tg negative and TBS still
positive due to cervical remnants (20 patients), lymph node uptake (one) and metastasis (five); 20 patients remained Tg and
TBS positive, but 14 of them only showed thyroid remnants.

Conclusions  We propose to perform periodic diagnostic TBS to improve Tg specificity, at least while neck thyroid activity is detected,
even if Tg is negative.

Content Type Journal ArticleCategory Original articleDOI 10.1007/s00259-008-0789-yAuthors
Elisa Caballero-Calabuig, Hospital Universitario Dr. Peset—Medicina Nuclear Avda. Gaspar Aguilar, 90 Valencia Valencia 46017 SpainCarmen Cano-Terol, Hospital Universitario Dr. Peset—Medicina Nuclear Avda. Gaspar Aguilar, 90 Valencia Valencia 46017 SpainRamón Sopena-Monforte, Hospital Universitario Dr. Peset—Medicina Nuclear Avda. Gaspar Aguilar, 90 Valencia Valencia 46017 SpainDolores Reyes-Ojeda, Hospital Universitario Dr. Peset—Medicina Nuclear Avda. Gaspar Aguilar, 90 Valencia Valencia 46017 SpainPedro Abreu-Sánchez, Hospital Universitario Dr. Peset—Medicina Nuclear Avda. Gaspar Aguilar, 90 Valencia Valencia 46017 SpainJosé Ferrer-Rebolleda, Hospital Universitario Dr. Peset—Medicina Nuclear Avda. Gaspar Aguilar, 90 Valencia Valencia 46017 SpainPablo Sopena-Novales, Hospital Universitario Dr. Peset—Medicina Nuclear Avda. Gaspar Aguilar, 90 Valencia Valencia 46017 SpainCarmen Plancha-Mansanet, Hospital Universitario Dr. Peset—Medicina Nuclear Avda. Gaspar Aguilar, 90 Valencia Valencia 46017 SpainJesús Félix-Fontestad, Hospital Universitario Dr. Peset—Medicina Nuclear Avda. Gaspar Aguilar, 90 Valencia Valencia 46017 Spain

Journal European Journal of Nuclear Medicine and Molecular ImagingOnline ISSN 1619-7089Print ISSN 1619-7070 (Source: European Journal of Nuclear Medicine and Molecular Imaging)