Endocrine Abstracts

Introduction: The presence of undetectable serum levels of stimulated thyroglobulin (Tg) with negative imaging tests is the criterion used to define remission in low-risk differentiated thyroid cancer (DTC). Most guidelines recommend 131-I ablation after thyroidectomy to remove any possible residual thyroid tissue. Our aim was to know how often undetectable Tg levels are achieved before ablation to avoid unnecessary radiation treatments.

Patients and methods: One hundred and eighteen patients (106 women and twelve men, age 15–83 years) with low-risk DTC who underwent total thyroidectomy from 2005 to 2011were included. Tg, anti-Tg antibodies (TgAb) and TSH were analysed before and the fifth day after a dose of recombinant human TSH administration. They were measured in an Inmmulite® 2000 (Tg functional sensitivity: 0.9 ng/ml) 6–18 weeks after the surgery. Subsequently, a dose of 100 mCi of 131-I was administered to all patients and other possible treatments were applied when necessary. A correlation between postoperative stimulated Tg concentration and clinical situation at the end of the follow-up (25.6±15.6 months) was performed.

Results: Eleven patients with positive TgAb were excluded. Tg levels were undetectable in 50 patients (47%), 1–10 ng/ml in 42 (39%) and >10 ng /ml in 15 (14%). At the end of the study, there was no evidence of recurrence in the 50 patients with undetectable postoperative Tg. Remission criteria were met in 39/42 and 9/15 patients with Tg between 1–10 and >10 ng/ml, respectively.

Conclusions: In near half of the patients with low risk DTC 131-I therapy is not necessary to achieve undetectable Tg levels after total thyroidectomy. An undetectable postoperative stimulated Tg predicts the absence of recurrence during the long term follow-up. 131-I ablation should not be necessarily performed in all the patients with low-risk DTC.