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.

BACKGROUND: This study was conducted to identify the relevant cutoff value and to evaluate the usefulness of postoperative-stimulated serum thyroglobulin (Tg) at the time of (131)I ablation for the prediction of disease status in patients with differentiated thyroid carcinoma (DTC) who received high-dose (131)I ablation therapy after total thyroidectomy.

METHODS: We analyzed 218 consecutively enrolled patients who were diagnosed with DTC and underwent total thyroidectomy. All patients underwent (131)I ablation at doses of 100-200 mCi, and stimulated serum Tg was measured at the time of (131)I ablation therapy. To assess disease-free status after (131)I ablation therapy, stimulated serum Tg levels, diagnostic whole-body scan (DxWBS) and neck ultrasonography (US) were performed 6-12 months after (131)I ablation.

RESULTS: The 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.

CONCLUSION: Postoperative-stimulated Tg at the time of (131)I remnant ablation is a useful biochemical marker for the prediction of disease status in patients with DTC. When high-dose (131)I remnant ablation is performed after total thyroidectomy, the stimulated Tg measurement and DxWBS that are usually performed 6-12 months after (131)I 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.