Differentiated Thyroid Carcinoma Presenting With Distant Metastasis at Initial Diagnosis

Abstract

Distant metastasis (DM) is seldom observed at initial presentation of differentiated thyroid carcinoma (DTC), making it difficult to assess the clinical characteristics and treatment outcomes of DTC patients with DM. We therefore retrospectively assessed these parameters in DTC patients who presented with DM between July 1994 and December 2007. In addition, we compared biologic behaviors and prognostic factors between patients presenting with DM and those developing DM after initial treatment. Among 1560 DTC patients who underwent thyroidectomies during the 13.5-year study period, 91 patients were included in this study; 52 patients (3.4%) displayed DM at initial presentation and 39 (2.5%) developed DM after initial 131 radiacitive iodine (RI) treatment. Metastatic lesions were treated with high dose RI (94.5%), surgical resection (14.3%), external beam radiation therapy (31.9%), embolization of feeding vessels (1.1%), and/or chemotherapy (1.1%). Median duration of follow-up was 75 months (range, 12-158 months). Mean patient age was 57 years (range, 13-80 years), and the female-to-male ratio was 2.03:1. Metastases were detected in the lung only (68.1%), bone only (16.5%), and multiple sites (15.4%). When clinical and tumor characteristics were considered, metastatic lesion iodine avidity was significantly higher in patients presenting with DM. At 5 and 10 years, the overall survival (OS) rates in patients presenting with DM were 83.8% and 72.1%, respectively, and the disease-specific survival (DSS) rates were 68.5% and 26.8%. OS did not differ significantly between patients presenting with DM and those developing DM after initial treatment. However, those with initial DM enjoyed significantly improved DSS compared with patients who developed DM after initial treatment. At last follow-up, 22 patients (24.2%) were alive without disease, 48 (52.7%) were alive with disease, and 21 (23.1%) had died of disease in study patients. Multivariate Cox's regression analyses showed that complete local control was a significant predictor of OS and DSS in all study patients. In patients developing DM after initial treatment, metastatic lesion iodine avidity was also associated with both OS and DSS. In contrast, avidity was associated only with DSS in patients presenting with DM. Our study showed that DTC patients presenting with initial DM appear to have relatively favorable outcomes compared with DTC patients who developed DM after initial treatment. Complete local control may be the most important prognostic indicator in all DM patients. Metastatic lesion iodine avidity had a significant impact on both OS and DSS in patients developing DM after initial treatment, but significantly influenced only DSS in patients presenting with initial DM.