| ObjectThyroid cancer (TC) is the most common malignant tumor of endocrine system, with a significant increasing prevalence worldwide. Differentiated thyroid cancer (DTC) accounts for 90% of all thyroid cancers. The rate of distant metastatic DTC is 7-12%. Treatment for thyroid cancer is predominantly surgical approach accompanied with radioactive iodine (RAI) ablation of the thyroid remnant or distant metastasis and TSH suppression using levothyroxine which results a 90% rate of 5-year survival. However, the patients insensitive to RAI therapy have<50% and<10% rate of 5-year and 10-year survival respectively. Recently, RAI-refractory DTC have become the research focus. There is a clear definition of RAI-refractory DTC in 2015 American Thyroid Association Management Guidelines for Adult Patients with Thyroid Nodules and Differentiated Thyroid Cancer. However, clinical research of RAI-refractory DTC have not been reported in China. This study provid a retrospective analysis on the RAI-refractory DTC patients in Qilu Hospital of Shandong University, and try to summarize some clinical features, to estimate their survival rate, and to find correlative clinical factors of RAI-refractory DTC.MethodA single-center retrospective observational study is conducted in distant metastatic DTC patients submitted to radioactive iodine treatment in the department of radionuclide therapeutics of Qilu Hospital from Jan 2002 to Sep 2015. Patients’ clinical information including clinical manifestation, pathologic results and medical imaging is recorded. According to the definition of RAI-refractory DTC in 2015 American Thyroid Association Management Guidelines for Adult Patients with Thyroid Nodules and Differentiated Thyroid Cancer, we divide distant metastatic DTC into two subgroups, including RAI-refractory DTC and RAI-efficient DTC. Follow-up is performed by telephone. Survival analysis is conducted by Kaplan-Meier and log-rank test. Univariate analysis of enumeration data and measurement data is performed by t test and Chi-square test, including sex, age of distant metastasis, pathological type, primary lesion (size, unilateral or bilateral lesion, tissue infiltration), numbers and TNM staging of cervical lymph node metastasis, situation of mediastinal lymph node metastasis, site of distant metastasis, iodine uptake rate of 2 hours and accompanied benign thyroid disease. Multivariate analysis of correlative factors is performed by logistic regression analysis. All the analysis is conducted with SPSS (version 22.0; IBM SPSS, Armonk, NY, USA), and the quantitative data is presented as the mean ± standard deviation.p<0.05 is considered to indicate a statistically significant difference.Result1. We find 77 patients with distant metastasis in all 1077 cases. Among these patients,25 (2.32%) are identified as RAI-refractory DTC with an average age of (56.24±15.96) years old, median age of 57 years old, and a male-to female ratio of 1:2.57.2. The 3-year and 5-year survival rate of the 25 RAI-refractory DTC patients is 75% and 62%. The survival of RAI-refractory DTC is significantly worse than RAI-efficient DTC (p=0.001).3. Univariate analysis shows that age of distant metastasis older than 45 years (p=0.004) and pathological type of FTC (p=0.009) are two risk factors related to RAI-refractoriness. But the following factors are not related, including:sex (p=0.883), size of primary lesion (p=0.633), unilateral or bilateral lesion (p=0.482), tissue infiltration (p=0.369), numbers (p=0.677) and TNM staging (p=0.571) of the metastatic lymph nodes, mediastinal lymph node metastasis (p=0.299), metastatic site (p=0.145), iodine uptake rate of 2 hours (p=0.272) and accompanied benign thyroid disease (p=0.270). Logistic regression analysis indicates that age of distant metastasis older than 45 years (p=0.012, OR=5.431, 95% CI:1.456-20.251) and pathological type of FTC (p=0.040, OR=4.485,95% CI:1.070-18.808) are the independent risk factors for RAI-refractory DTC.Conclusion1. In the DTC patients with 131I treatment, the rate of RAI-refractory DTC is very low, just 2.32%. Females of RAI-refractory DTC are more than males.2. The survival of RAI-refractory DTC was significantly worse than those RAI-efficient DTC.3. Logistic regression analysis indicates that age of distant metastasis older than 45 years and pathological type of FTC are independent risk factors of RAI-refractory DTC. |
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