Postoperative-stimulated serum thyroglobulin measured at the time of 131I ablation is useful for the prediction of disease status in patients with differentiated thyroid carcinoma

BackgroundThis study was conducted to identify the relevant cutoff value and to evaluate the usefulness of postoperative-stimulated serum thyroglobulin (Tg) at the time of 131I ablation for the prediction of disease status in patients with differentiated thyroid carcinoma (DTC) who received high-dose 131I ablation therapy after total thyroidectomy.MethodsWe analyzed 218 consecutively enrolled patients who were diagnosed with DTC and underwent total thyroidectomy. All patients underwent 131I ablation at doses of 100–200 mCi, and stimulated serum Tg was measured at the time of 131I ablation therapy. To assess disease-free status after 131I ablation therapy, stimulated serum Tg levels, diagnostic whole-body scan (DxWBS) and neck ultrasonography (US) were performed 6–12 months after 131I ablation.ResultsThe relevant cutoff value of postoperative stimulated Tg for the prediction of disease-free status was 2 ng/mL. A total of 138 patients (63.3%) showed values of <2 ng/mL. Postoperative-stimulated Tg < 2 ng/mL had a negative predictive value of 94.9%, which increased to 97.7% when low Tg was combined with negative neck US findings.ConclusionPostoperative-stimulated Tg at the time of 131I remnant ablation is a useful biochemical marker for the prediction of disease status in patients with DTC. When high-dose 131I remnant ablation is performed after total thyroidectomy, the stimulated Tg measurement and DxWBS that are usually performed 6–12 months after 131I ablation therapy may be skipped, at least in low- and intermediate-risk patients with postoperative stimulated Tg of < 2 ng/mL and negative neck US findings.