Assessment of risk factors in metastatic/recurrent tall cell variant of papillary thyroid carcinoma

Abstract

Introduction: Papillary thyroid carcinoma (PTC) is the most common malignant thyroid tumour. A great majority of the cases live a disease-free life with quite favourable prognosis. There are lots of variants of PTC, and a few of them exhibit aggressive behaviour. A typical example is the tall cell variant (TCV). Patients experience a greater incidence of recurrence, nodal and extranodal metastases, and tumour-associated mortality than in other variants of PTC. Studies related to TCV almost always compared it with its patient population of PTC according to risk factors and clinicopathological features. The aim of this study is to evaluate the risk factors in metastatic/recurrent TCV. Materials and methods: This is a retrospective cohort study of 1813 patients with differentiated thyroid carcinoma treated with radioiodine between 1992 and 2011. Fifty-six of these patients are TCV. Thirty-four of them developed metastasis/recurrence, and 22 lived a disease-free life during a follow-up time of 4-23 years. We evaluated the risk factors in these metastatic and non-metastatic subgroups. Results: We found tumour size, pre-ablation thyroglobulin level, vascular invasion, preablation central and lateral cervical lymph node metastasis, pre-ablation lung metastasis, and stage-independent risk factors. However, age, pre-ablation thyroglobulin level, and stage appeared together as striking factors impacting metastasis in multivariate analysis. Conclusion: Higher ablation doses up to 250-300 mCi should be administered to TCV patients having advanced stage (III, IV), moderately high pre-ablation thyroglobulin level (over 400 ng/ml), and older age (over 52 years) especially with large tumour size (over 3.5 cm) and initial cervical lymph node metastasis.