Serial Thyroglobulin Variation Trend Shortly after Radioiodine Therapy in Poorly to Moderately Differentiated Recurrent Thyroid Cancer.

Objective To dynamically observe the early change of thyroglobulin(Tg) levels after (131)I therapy in differentiated thyroid cancer(DTC) patients. Methods The study enrolled 22 post-total-thyroidectomy DTC patients and they were stratified as low to intermediate recurrence according to the 2009 American Thyroid Association Guidelines. The clinical data including pre-ablation stimulated Tg (ps-Tg),corresponding thyroid stimulating hormone(TSH),anti-thyroglobulin (TgAb) values,and the afterwards parameters were dynamically measured each week in the first month after (131)I therapy. Values collected at the first time were defined as Tg 0 and TSH0,while Tg1 and TSH1 were collected at the first week after (131)I therapy respectively. Then the variation trend curves of Tg were drawn,and factors influencing the variation of Tg were analyzed. Two groups were divided according to Tg levels:G1 (Tg≤0.1 ng/ml,n=9) and G2(Tg>0.1 ng/ml,n=13). Results The rates of negative Tg were 4.5%,18.0%,27.0%,36.0%,and 41.0%,respectively,exactly before (131)I therapy and the 1(st),2(nd),3(rd),and 4(th) week after the therapy. One-way analysis of variance showed that the two groups statistically differed in age (F=3.182,P=0.04) and remnant thyroid (U=4.849,P=0.026). Multivariate logistic regression analysis showed that early negative Tg was related to remnant thyroid tissue (OR:2.132;95%Cl:1.418- 6.532,P=0.009). Conclusions Negative Tg can be achieved in nearly half of DTC patients by the end of first month after (131)I therapy. The negative conversion is closely related with the volume of remnant thyroid tissue.