Risk factors associated with high thyroglobulin level following radioactive iodine ablation, measured 12 months after treatment for papillary thyroid carcinoma

PURPOSE: The measurement of serum thyroglobulin (Tg) of papillary thyroid carcinoma patients, 12 months after total thyroidectomy and radioactive iodine (RAI) ablation following thyroxine hormone withdrawal (T4-off Tg) or recombinant human thyroid-stimulating hormone stimulation (rhTSH-Tg), is standard method for monitoring disease status. The aim of this study was to find predictive factors for detectable T4-off Tg during follow-up. METHODS: A retrospective review was conducted of 329 patients who underwent total thyroidectomy and RAI ablation between October 2008 and August 2012. Subjects were assigned to high (>1 ng/mL, n = 53) and low (≤1 ng/mL, n = 276) groups, based on T4-off Tg measured 12 months postoperatively. Demographic and clinicopathological characteristics at diagnosis and follow-up were compared between the 2 groups. RESULTS: The low and high T4-off Tg groups differed with respect to tumor size, preoperative Tg, ablative Tg, cervical lymph node metastasis, thyroglobulinemia out of proportion to results of diagnostic whole body scan, and American Thyroid Association 3-level stratification and restratification. Multivariate analysis confirmed that ablative Tg > 1.0 ng/mL (odds ratio [OR], 10.801; P = 0.001), more than 5 cervical lymph node metastasis (OR, 6.491; P = 0.003), and thyroglobulinemia out of proportion (OR, 9.221; P = 0.000) were risk factors. CONCLUSION: Ablative Tg >1.0 ng/mL, more than 5 cervical lymph node metastasis, and thyroglobulinemia out of proportion were independent factors for T4-off Tg >1 ng/mL 12 months postoperative. In low-risk patients without these risk factors, the possible omission of Tg measurements could be considered during follow-up.