Low postoperative nonstimulated thyroglobulin as a criterion to spare radioiodine ablation

This study evaluated the recurrence rate in patients with papillary thyroid carcinoma (PTC) who had low nonstimulated thyroglobulin (Tg), measured with a second-generation assay, after total thyroidectomy and who were not submitted to ablation with I-131. The objective was to define whether low postoperative nonstimulated Tg can be used as a criterion to spare patients with PTC from therapy with I-131. This was a prospective study including 222 patients with PTC (except for microcarcinoma restricted to the thyroid and tumor with extensive extrathyroid invasion (pT4), aggressive histology, extensive lymph node (LN) involvement, or known residual disease). After thyroidectomy, all patients had nonstimulated Tg < 0.3 ng/ml, negative antithyroglobulin antibodies (TgAb) and neck ultrasonography (US) showing no anomalies. Because of this finding, the patients were not submitted to ablation with I-131. The time of follow-up ranged from 15 to 102 months (median 62 months). Of the 222 patients, 217 (97.7%) continued to have nonstimulated Tg < 0.3 ng/ml and negative US. Tg was undetectable in the last assessment in 185 of these patients and detectable in 32. Five patients (2.2%) exhibited an increase in Tg, and LN metastases were detected in 4 (structural recurrence). One patient progressed to an increase in Tg, but disease was not detected by the imaging methods (biochemical recurrence). The results obtained here suggest that patients with PTC who have low nonstimulated Tg (measured with a second-generation assay and in the absence of TgAb) and negative neck US after thyroidectomy do not require ablation with I-131.