Abstract
Simple SummaryThe prognostic significance of metastatic sites, and immediate cause of death in MTC patients with distant metastasis remains unclear. In this study, we calculated the time from metastasis to death, and we found that long-term oncologic outcomes were differ from initial metastatic site; the hazard ratio for bone metastatic sites (HR: 5.42; p = 0.044) and multisite metastasis (HR: 6.11; p = 0.006) were significantly higher than for lung metastasis. Complications due to the progression of distant metastasis were the most common cause of death, followed by complications related to chemotherapy and airway obstruction.Distant metastasis is a poor prognostic factor in medullary thyroid carcinoma (MTC), but the significance of differentiating the characteristics according to the site of distant metastasis remains unclear. This study aimed to evaluate the clinical characteristics and long-term oncologic outcomes in MTC patients with distant metastasis. We identified 46 MTC patients with distant metastasis between 1994 and 2019. Clinical characteristics were compared based on the timing of the detection of distant metastasis. Additionally, survival rates following the detection of distant metastasis were evaluated to compare the clinical significance of metastatic site. The detailed causes of death were also investigated. Of the 46 patients, 15 patients (32.6%) had synchronous distant metastasis and 31 patients (67.4%) had metachronous distant metastasis. There was no clinical difference between these two groups except regarding initial surgical extent. The lung (52.2%) was the most common metastatic site, followed by the bone (28.3%), mediastinum (19.6%), liver (17.4%), adrenal gland (4.3%), brain (4.3%), kidney (2.2%), and pancreas (2.2%). Patients with bone metastasis and multisite metastasis had significantly worse prognoses than those with lung metastasis (hazard ratio: 5.42; p = 0.044 and hazard ratio: 6.11; p = 0.006). Complications due to the progression of distant metastasis, airway obstruction due to tracheal invasion, and complications related to chemotherapy were leading causes of death. In conclusion, there was no difference in clinical characteristics according to the timing of distant metastasis. Oncological outcomes differed by metastatic site.
Highlights
Medullary thyroid carcinoma (MTC) is an uncommon disease derived from the parafollicular cells of the thyroid gland [1]
We focused on MTC patients with distant metastasis; survival rates were evaluated only for MTC patients with distant metastasis, not for all MTC patients
Distant metastasis was found in 19% of MTC patients during a mean follow-up period of 9.7 years, with one-third of cases confirmed at the initial diagnosis and two-thirds of cases confirmed during the follow-up period
Summary
Medullary thyroid carcinoma (MTC) is an uncommon disease derived from the parafollicular cells of the thyroid gland [1]. It occurs either sporadically or in a hereditary form and accounts for 1% to 2% of all thyroid carcinoma cases in the United States and 0.6% of all cases in Korea [2,3]. MTC presents with locoregional metastasis in 50% of patients and distant metastasis in 10% to 15% of patients at the time of initial diagnosis [4]. Unlike patients with DTC, those with MTC are not eligible to receive radioactive iodine therapy; MTC with distant metastasis is incurable [7]. The lungs, liver, and bone are common metastatic sites, and distant metastasis is known to be a poor prognostic factor for long-term oncologic outcomes [9,12,13,14]
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