Predictive value of the stimulated thyroglobulin before and after 131I therapy for curative effect in patients with papillary thyroid carcinoma

Abstract

Objective To analyze the stimulated thyroglobulin (sTg) level and variation tendency before and after 131I therapy in papillary thyroid carcinoma (PTC), and evaluate the predictive value of sTg for the efficacy of 131I therapy. Methods From January 2013 to September 2016, a total of 178 PTC patients (53 males, 125 females; average age (44.1±11.4) years) without distant metastases who received 131I treatment in Tianjin Medical University General Hospital were reviewed. The patients were divided into two groups: group 1 (n=23) with residual thyroid detected by 131I whole body scan (WBS) and group 2 (n=155) without residual thyroid. Both thyroid stimulating hormone (TSH) and sTg were measured and defined as TSH1, sTg1 before 131I therapy, and TSH2, sTg2 after 131I therapy. Data of the two groups were compared with two-sample t test, χ2 test and Mann-Whitney u test. The receiver operating characteristic (ROC) curve and diagnostic critical point (DCP) were used to evaluate the predictive value of sTg in radioiodine ablation efficacy. Results There were no significant differences in age (t=1.007), gender (χ2=1.419), tumor diameter (u=1 385), multifocal cancer (χ2=0.371), extrathyroidal extension (χ2=0.020) or lymph node metastasis (χ2=0.391, all P>0.05) between group 1 and group 2. The levels of sTg1 and sTg2 of group 1 were 6.3(2.0, 16.9) and 1.7(0.8, 4.2) μg/L, which were higher than those of group 2 (2.7(0.6, 6.4) and 0.3(0.2, 1.3) μg/L; u=1 118.5, 817.0, both P 0.05). The area under ROC curve, DCP, sensitivity, specificity, positive predictive value, and negative predictive value of sTg1 were 0.686, 4.435 μg/L, 60.9%(14/23), 67.7%(105/155), 21.9% (14/64) and 92.1%(105/144), respectively. Meanwhile, the parameters of sTg2 were 0.771, 0.460 μg/L, 91.3%(21/23), 58.1%(90/155), 24.4%(21/86) and 97.8%(90/92), respectively. Conclusions The level of sTg could be used to predict the efficacy of 131I therapy in PTC patients. Preablative sTg1 (<4.435 μg/L) or postablative sTg2 (<0.460 μg/L) holds high negative predictive value in identifying the efficacy of single 131I therapy. Key words: Thyroid neoplasms; Radiotherapy; Iodine radioisotopes; Thyroglobulin