Recombinant human thyrotropin-stimulated thyroglobulin level at the time of radioactive iodine ablation is an independent prognostic marker of differentiated thyroid carcinoma in the setting of prophylactic central neck dissection.

Abstract

We investigated the value of the stimulated thyroglobulin (Tg) level at the time of recombinant human thyrotropin (rhTSH)-aided remnant ablation for predicting disease status 1year later in patients with DTC who underwent total thyroidectomy with central neck dissection (CND). This was a prospective observational study of 253 consecutive patients with DTC who underwent rhTSH-aided RAI ablation after total thyroidectomy and prophylactic CND. Patients with evidence of initial distant metastasis or positive Tg antibodies were excluded. We compared rhTSH-stimulated Tg level at RAI ablation according to the disease status at 1year and evaluated optimal cut-off value of rhTSH-stimulated Tg. Binary logistic regression analysis was performed to investigate the independent predictive factors for disease status 1year after ablation. Among study participants, 228 (90·1%) were considered disease free at 1year after remnant ablation. Patients with persistent or recurrent disease were more likely to be aged ≥45years, and to have N1b stage, TNM stage III or IV, and higher rhTSH-stimulated Tg level at RAI ablation. The optimal cut-off of rhTSH-stimulated Tg for predicting persistent or recurrent disease was 1·79ng/ml, with a negative predictive value of 99·5%. A serum rhTSH-stimulated Tg level ≥1·79 at the time of ablation was independently associated with persistent or recurrent disease 1year later. N1b stage tended to be associated with persistent or recurrent disease. A low stimulated serum Tg level at rhTSH-aided RAI ablation may be a favourable prognostic marker in the setting of prophylactic CND.