RESULTS OF INDIVIDUAL RADIOIODINE DOSE CALCULATION IN HYPERTHYREOIDISM.

Aim: A total of 154 patients with hyperthyroidism received 161 individually calculated radioiodine treatments between October 2004 and December 2005. M/F ratio was 25/129, age distribution: 26-87 years, mean age: 60 years. Forty-six patients had toxic adenoma, 25 patients were treated with toxic multinodular goiter, 83 patients with Graves’ disease. Material and methods: The target dose was calculated according to the etiology of hyperthyroidism: 350 Gy in toxic adenoma, 150 Gy in toxic multinodular goiter and 70–100 Gy in Graves’ disease depending on the size and nodularity of the thyroid. The estimate of the thyroid mass was based on the scintigraphy, the calculation of the biological half life was simplified by the late iodine uptake (7. day) measurement, according to the previous investigations. The activity of radioiodine was calculated by the following formula: 3.5 x thyroid mass (g) x target dose (Gy)/ /late iodine uptake (%). Results: The average radioiodine dose was 378 MBq (min. 100, max. 1180, 1. quartilis 230, median 340, 3. quartilis 500 MBq). Six and 12 months after the treatment, follow-up data were available in 91% and 83% of patients, respectively. The hypothyroidism/euthyroidism/hyperthyroidism ratio was 23/51/26% 6 months and 22/49/16% 12 months after the radioiodine treatment. Eighteen hyperthyroid patients at the 6-month follow-up were selected for a second radioiodine treatment, these patients were not evaluated during the 12-month control. According to the etiology of thyrotoxicosis, the distribution of hypo/eu/hyperthyroidism at the 6-month followup was 11/80/9% in toxic adenoma, 5/52/43% in toxic multinodular goiter, 35/35/ /30% in Graves’ disease, respectively. Conclusion: Our dose-calculation method resulted in excellent success rate in toxic adenomas, good success rate in Graves’ disease even in international comparison but the results were not satisfactory in toxic multinodular goiters. Difficulties to determine the targeted thyroid mass in this entity may be responsible for the treatment failure. [ABSTRACT FROM AUTHOR]