A low postoperative nonstimulated serum thyroglobulin level excludes the presence of persistent disease in low-risk papillary thyroid cancer patients: implication for radioiodine indication

Objective To evaluate the presence of persistent disease, including on post-therapy whole-body scan (RxWBS), in low-risk patients with papillary thyroid carcinoma (PTC) > 1 cm who have low nonstimulated thyroglobulin (Tg) (measured with a sensitive assay), negative anti-Tg antibodies (TgAb) and neck ultrasound (US) showing no metastases after total thyroidectomy. Patients We studied 154 patients with PTC > 1 cm classified as low risk, who had US without metastases, negative TgAb, nonstimulated Tg <= 0.25 ng/ml and TSH <= 2 mIU/l about 3 months after total thyroidectomy. Results Tg measured immediately before I-131 was <= 1 ng/ml in 89.5% of the patients and > 1 ng/ml in 10.5%. None of the patients showed ectopic uptake on RxWBS. Uptake in the thyroid bed was observed in 146 (94.8%) patients and was <= 2% in all of them. In the control assessment 9-12 months after ablation, stimulated Tg (sTg) <= 1 ng/ml was achieved in 150 patients (97.4%). Only one patient had sTg > 2 ng/ml (2 .5 ng/ml) and none of the patients had apparent disease detected by imaging methods. During further short-term follow-up after control assessment (median of 24 months), none of the patients had tumour recurrence. Conclusions The combination of nonstimulated Tg <= 0.25 ng/ml, negative TgAb and US without metastases after thyroidectomy rules out the presence of persistent disease (including on RxWBS) in low-risk patients with PTC > 1 cm. This demonstration weakens the indication of ablation with I-131 in these cases.