Relationship between Variation of Pre-ablation Stimulated Thyroglobulin and Distant Metastasis in Patients with Differentiated Thyroid Cancer.

Objective: To investigate the relationship between the dynamic variation of pre-ablation stimulated thyroglobulin(sTg)and distant metastasis in patietns with differentiated thyroid cancer(DTC).

Methods: DTC patients after total or near total thyroidectomy were divided into two groups as M1 group(n=38)and M0 group(n=130)according to the presence of distant metastases or not. Clinical data including pre-ablation sTg and the corresponding thyrotropin(TSH)values were dynamically measured. The pre-ablation sTg and corresponding TSH collected at the first time were defined as Tg1 and TSH1,while as Tg2 and TSH2 at the last time. χ(2) test was used to compare the variation tendency of sTg between these two groups. Tg1,Tg2,pre-ablation sTg variation(∆Tg),and ∆Tg/∆TSH ratio between M0 and M1 were compared by Mann-Whitney rank-sum test. The receiver operating characteristic(ROC)curves and diagnostic critical point(DCP)were employed to evaluate the predictive values of the above indicators.

Results: Both Tg1 and Tg2 of M1 were significantly higher than those of M0(the Mann-Whitney rank-sum test:Tg1 P<0.001,Tg2 P<0.001). The corresponding areas under the ROC curve(AUC)to differentiate the two groups were 0.921 and 0.942,respectively. The cut-off value of Tg2,which was more accurate in predicting distant metastasis,was 24.3 ng/ml with a sensitivity of 92.11% and a specificity of 83.85%. Both ∆Tg and ∆Tg/∆TSH between these two groups were significantly different(the Mann-Whitney rank-sum test:∆Tg P=0.002,∆Tg/∆TSH P<0.001). ∆Tg/∆TSH worked better than Tg2 in predicting distant metastasis with both higher accuracy(87.50%)and higher specificity(86.92%).

Conclusions: Dynamically tracing pre-ablation sTg may improve the accuracy and specificity of distant metastases prediction in DTC patients. ∆Tg/∆TSH,which means the ratio of sTg variation to TSH variation,may be a useful diagnostic marker for predicting distant metastases in DTC.