Endocrine Abstracts

Background: Previous studies have suggested that serum thyroglobulin (Tg) levels at the time of 131I remnant ablation just after thyroidectomy, could be a prognostic tumor marker in differentiated thyroid cancer (DTC).

Objective: The aim of this study was to evaluate if serum preablation Tg in the earliest postoperative period could be useful for predicting persistence or recurrence of disease.

Methods: This study was a retrospective analysis. We included 160 patients with DTC who underwent total thyroidectomy and received ablative therapy with I131 from January 2000 to December 2011. A stimulated Tg was measured just at the time of the first 131I therapy (preablation-Tg). We correlated this value with a stimulated Tg-control (control-Tg) measured at the time of the diagnostic whole-body scan, performed approximately 6–12 months after preablation-Tg. Exclusion criteria were positive Tg antibody (n=9) and microcarcinoma (n=26). Follow-up was performed according to the American Thyroid Association Guidelines published in 2009. The minimum follow-up period was 14 months.

Results: Sixty-three of 77 patients (82%) with preablation-Tg ≤3 ng/ml showed undetectable (≤1 ng/ml) control-Tg and 37 of 48 (77%) patients with preablation-Tg >3 ng/ml showed detectable (>1 ng/ml) control-Tg (P<0.001). At follow-up, 72 of 91 (79%) with preablation-Tg ≤3 ng/ml showed remission and 20 of 28 patients (71%) who showed persistence/recurrence, had a preablation-Tg >10 ng/ml (P<0.001). The negative predictive value for recurrence in patients having preablation-Tg ≤3 ng/ml was found to be 98.4% (73 of 77 patients, P<0.001).

Conclusion: Preablation-Tg levels correlated well with the control-Tg levels. A preablation-Tg ≤3 ng/ml is a favorable prognostic factor in DTC.