Radioiodine I-131 Therapy In Low Risk Well Differentiated Thyroid Carcinoma: Comparison Between Fixed Doses Versus Variable Doses Based on Tc-99m Pertechnetate Uptake Rate
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Date
2017-05
Authors
Majidi, Rahmat
Journal Title
Journal ISSN
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Publisher
Universiti Sains Malaysia
Abstract
Introduction: Total thyroidectomy, followed by radioiodine-131 to destroy any remaining thyroid cell or thyroid cancer cell, is an established method of treatment for thyroid carcinoma. Based on ATA 2009 guideline, dose activity of radioiodine-131 between 30 to 100 mCi is recommended in low risk well differentiated thyroid carcinoma.
Objective: The aim of this study is to compare the success rate of fixed dose radioiodine-131 therapy against variable doses based on thyroid Tc-99m pertechnetate uptake rate in treatment of low risk well differentiated thyroid carcinoma.
Method: 53 patients (47 female and 6 male; mean + SD = 41.3 + 13 years) diagnosed with well differentiated thyroid carcinoma with N0 and M0 disease who had undergone total thyroidectomy were evaluated prospectively. They were randomly divided into two groups according to fixed doses (80 mCi) and variable doses (30 mCi, 80 mCi or 100 mCi) of radioiodine-131 based on thyroid Tc-99m pertechnetate uptake rate (n = 27 for fixed dose group, n = 26 for variable dose). All patients underwent radioiodine-131 ablation therapy followed by radioiodine-131 WBS and stimulated serum thyroglobulin monitoring to evaluate the outcome after 12 months.
Result: At 12 months, 19 (36%) patients were successfully ablated after received single dose of radioiodine-131 ablation. In the fixed dose group, 11 out of 27 (41%) patients were successfully ablated compare to variable group with 8 out of 26 patients (31%). However, the differences were statistically not significant (p = 0.573). Pre-treatment stimulated serum thyroglobulin less than 2 ug/L and duration of less than 4 months to first radioiodine-131 were associated with higher chance of successful ablation. There were no significant differences in success rates in term of age, sex, race, or histological type of primary tumour.
Conclusion: There is no significant differences in success rate between the fixed dose protocols against variable dose in remnant ablation in with low risk well differentiated thyroid carcinoma. There may be value of thyroid Tc-99m pertechnetate uptake study especially in those patients with uptake rate >1.4% who may require higher dose of radioiodine-131 to achieve success rate after one administration. Further studies with a larger sample size and covering other contributing factors are recommended.
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Keywords
Total thyroidectomy, followed by radioiodine-131 , is an established method of treatment for thyroid carcinoma