Postoperative-stimulated serum thyroglobulin levels measured just before the initial I-131ablation is useful for prediction of disease status in patients with low-risk differentiated thyroid cancer

Objectives we evaluated whether postoperative-stimulated serum thyroglobulin levels(Pre-Tg) measured just before the initial I-131 ablative therapy (IAT) could predict the disease status of the first IAT in patients with low-risk differentiated thyroid carcinoma (DTC).

Methods Patients with DTC (n=662) treated with total or near-total thyroidectomy followed by immediate IAT were studied. Patients with positive anti-Tg autoantibodies, not meet the low-risk criteria ,or with a recent history of iodine contamination were excluded. we used diagnostic whole-body scan (D-WBS) and thyroglobulin levels at the time of the firs D-WBS (Post-Tg) to identify disease status.

Results 158 patients left fulfilled the inclusion criteria and had no exclusion criteria. After the first D-WBS, Of 32 patients with Pre-Tg≤2µg/liter, 28 patients (87.5%) showed successful ablation, one patients(3.1%) was regarded as “equivocal”; and 3 patients (9.4%) showed persistent disease. Of 126 patients with Pre-Tg>2µg /liter, successful ablation was observed in 59 cases (46.8%), “equivocal” was observed in 32 cases (25.4%); and persistent disease was observed in 35 cases (27.8%). there was significant correlation between the level of Pre-Tg and the result of the initial IAT (three by three χ² test, χ² =33, df=4, P <0.001).

Conclusions Pre-Tg level could predict disease status of the first IAT in patients with low-risk DTC. We could use Pre-Tg level as an earlier parameter to predict disease status in patients with low-risk DTC.