Assessment of Risk Factors in Metastatic / Recurrent Tall Cell Variant of Papillary Thyroid Carcinoma

47 Objectives Papillary thyroid carcinoma (PTC) is the most common malignant thyroid tumor. A great majority of the cases live a disease-free life with quite favorable prognosis. There are lots of variants of PTC and a few of them exhibit aggressive behaviour. Typical example is the tall cell variant (TCV). Patients experience a greater incidence of recurrence, nodal and extranodal metastases, tumor associated mortality than those with PTC. Studies related to TCV almost always compared it with its patient population of PTC regarding to risk factors and clinicopathologic features. The aim of this study is to evaluate the risk factors in metastatic/recurrent TCV of PTC. Methods This is a retrospective cohort study of 1813 patients with differentiated thyroid carcinoma treated with radioiodine between 1992 and 2011. 56 of these patients are TCV. 34 of them developed metastasis/recurrence and 22 lived a disease-free life during the 23-year follow-up. We evaluated the risk factors in these metastatic and nonmetastatic subgroups. Results We found tumor size, preablation thyroglobulin level, vascular invasion, preablation central lymph node metastasis, preablation cervical lateral lymph node metastasis, preablation lung metastasis and stage as independent risk factors. However age, preablation thyroglobulin level and stage appeared as striking factors impacting metastasis together in multivariate analysis. Conclusions As possibly as highest ablation doses (up to 9250-11110 MBq (250-300 mCi) calculated according to quantitative tumor or blood/whole body dosimetry) should be applied to TCV especially having advanced stage (III, IV), pretty high preablation thyroglobulin level (over 300 ng/ml) and older age (over 51 years).