This study evaluated the long-term results of ablation with low iodine-131 (131I) activity in patients with papillary thyroid carcinoma (PTC) with a lower risk of recurrence and who remained with nonstimulated thyroglobulin (Tg) of at least 0.3 ng/ml after total thyroidectomy.Methods
This was a prospective study including 119 patients with PTC (except for microcarcinoma restricted to the thyroid and tumor with extensive extrathyroidal extension, aggressive histology, extensive lymph node involvement, or known residual disease). After thyroidectomy, all patients had nonstimulated Tg of at least 0.3 ng/ml (range: 0.3–8.5 ng/ml). The patients were treated with low 131I activity (30 or 50 mCi).Results
Post-therapy whole-body scanning showed ectopic uptake in two patients. When evaluated 12 months after ablation, nonstimulated Tg up to 0.2 ng/ml with negative antithyroglobulin antibodies and neck ultrasonography, defined as excellent response to initial therapy, was achieved in 92 patients (77.3%). Only one patient had persistent structural disease. During follow-up, 3/118 patients (2.5%) developed structural recurrence. In the last assessment, 102/115 patients who were not subjected to any additional therapy had nonstimulated Tg up to 0.2 ng/ml, negative antithyroglobulin antibodies, and ultrasonography with no anomalies. No death occurred because of the tumor.Conclusions
Postoperative nonstimulated Tg up to 2 ng/ml had a negative predictive value of 98% for recurrent or persistent structural disease. In patients with PTC who have a lower risk of recurrence and who remain with nonstimulated Tg of at least 0.3 ng/ml after total thyroidectomy, Tg up to 2 ng/ml can be used as a criterion for ablation with low 131I activity.