Abstract
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Objectives The aim of this study was to compare serum thyroglobulin (Tg) level measured just before and after recombinant human thyrotropin (rhTSH)-aided radioiodine ablative treatment (RIT) for predicting treatment response in patients with differentiated thyroid carcinoma (DTC).
Methods We enrolled 89 patients with DTC who underwent rhTSH-aided RIT (2.9-6.7 GBq) after total thyroidectomy. Serum Tg level was measured two times: 24 hours (early Tg) and 72 (or 96) hours (delay Tg) after the 2nd rhTSH injection. Excellent response was determined by the stimulated Tg levels <1 ng/mL with negative radioiodine uptake or suppressed Tg levels <0.2 ng/mL with negative neck ultrasonography after 8.3 ± 2.3 months of RIT. Univariate and multivariate analyses were done for early Tg, delay Tg, delta Tg (delay Tg - early Tg), ratio Tg (delay Tg: early Tg ratio), and other clinical and pathological variables (sex, age, TNM stage, tumor size, multicentricity, bilaterality, I-131 dose).
Results There were 44 (49.4%) excellent response patients. Univariate analysis showed that small tumor size (P=0.029), low early Tg levels (P=0.018) were significantly associated with excellent response. By multivariate analysis, early Tg level proved as the only independent predictor of excellent response (odds ratio [OR] = 1.944; 95% CI =1.167-3.240; P=0.011). Continuous variables (tumor size, early Tg and delay Tg) were stratified by cut-off values, according to ROC curve analysis. Of three candidate variables, early Tg level (OR = 17.854; 95% CI =2.711-117.582; P=0.003) only showed significance in predicting excellent response.
Conclusions Our data shows that the early Tg level may be used as a new prognostic indicator of treatment response in patients with DTC who underwent rhTSH-aided RIT. Tg should be measured just before RIT in rhTSH-aided RIT patients.