Prognostic Implications of Radioiodine Avidity and Serum Thyroglobulin in Differentiated Thyroid Carcinoma with Distant Metastasis

Although differentiated thyroid carcinoma (DTC) rarely develops distant metastases, the present study was performed to evaluate factors that affect the survival of patients with DTC who present with distant metastasis. Among 4,989 patients who underwent thyroid surgery for DTC, 82 presenting with distant metastasis were analyzed. Based on radioiodine (I-131) avidity and the thyroid-stimulating hormone-stimulated serum thyroglobulin (sTg) level at the time of metastasis, patients were divided into three groups: group 1 (I-131 uptake + sTg a parts per thousand currency sign 215 ng/mL, n = 46), group 2 (I-131 uptake + sTg > 215 ng/mL, n = 24), group 3 (no I-131 uptake, n = 12). Disease-specific survival (DSS) was estimated using the Kaplan-Meier method. Factors predicting the outcome were evaluated using Cox proportional hazard regression analysis. The age of patients (p = 0.04), frequency of follicular thyroid carcinoma (p = 0.002), tumor size (p < 0.001), and number of multiple metastatic sites (p = 0.004) differed significantly among the groups. With a median follow-up after surgery of 72 months, the 5- and 10-year DSSs for all patients were 84 and 69 %, respectively. The predictors of survival were age (p = 0.004), symptoms at the time of presentation (p = 0.045), histology (p = 0.01), sites of metastasis (p = 0.03), and I-131 avidity and sTg level at the time of metastasis (p = 0.002). In the multivariate analysis, age, histology, and I-131 avidity and sTg level at the time of metastasis remained significant factors for survival. Certain DTC patients with distant metastasis demonstrate favorable outcomes dependent on age, histology, and I-131 avidity and sTg level at the time of metastasis.