Objective: The aim of the present study was to evaluate the outcome of radioiodine treatment in thyrotoxicosis in childhood and adolescence.Methods: This was a retrospective study of 27 patients (ages 7.2- 19.8 years) with a diagnosis of thyrotoxicosis who received iodine-131 (I-131) treatment from January 2007 to December 2011 in the Nuclear Medicine Division, Department of Radiology, Faculty of Medicine, Chiang Mai University. Gender, duration of antithyroid drug (ATD) treatment, 24-hour I-131 uptake, thyroid weight, total dose and number of treatments with I-131, and thyroid status at 6 months after treatment were recorded.Results: The outcomes of 27 patients (85.2% female, 14.8% male) treated with radioactive iodine were analyzed to assess the effectiveness of therapy as related to dose and gland size. All children and adolescents received 150 µCi of I-131/g of thyroid tissue (n=27). Six 6 months after treatment, 44.5% of the patients were hyperthyroid, 14.8% were euthyroid, and 40.7% were hypothyroid. Of the 12 cases with hyperthyroidism, 2 cases needed a second dose of I-131 treatment, and they finally reached a hypothyroid state. The patients were classified into 2 groups according to treatment success (euthyroid and hypothyroid) and treatment failure (hyperthyroid). There were no significant differences in age, gender, duration of ATD treatment, 2- and 24-hour I-131 uptake, thyroid weight, and total I-131 dose between these two groups.Conclusions: Radioiodine treatment is safe and effective for thyrotoxicosis in childhood and adolescence. It is suitable as a good second-line therapy for patients with severe complications, those who show poor compliance, and those who fail to respond to ATD treatment. . Conflict of interest:None declared.

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The Suandok Model was a facility design that fulfilled requirements for the safe use of high radiation (131)I doses for thyroid cancer treatment in hospital. The facility presented in this study may not be suitable for all hospitals but the design concepts could be applied according to an individual hospital context and resources. People who use or gain benefit from radiation applications have to emphasise the responsibility to control and monitor radiation effects on individuals, communities and the environment.

Purpose: Currently, the advanced radiotherapy techniques such as Stereotactic radiotherapy (SRT) and Intensity modulated radiotherapy (IMRT) have been implemented in radiotherapy centers to improve the efficiency of cancer treatment. Due to their complexity, these techniques require the longer fraction delivery time comparing to conventional technique. This study aimed to prove a hypothesis that prolonged treatment time had a significant impact on cell sterilizing effect due to an increasing in DNA damage repair. Method and Materials: HeLa cells were irradiated by 6 MV linear accelerator using 3 different protocols simulated the advanced radiotherapy techniques. The absorbed dose of 200 cGy were given in 15, 30 and 45 min. Colony formation assay was used to determine cell survival while DNA damages were detected by Comet assay. The results were then compared to that of conventional technique with 5 min delivery time and analyzed by student T‐test. The Linear‐Quadratic model with α/β ratio and repair half‐time taken into account was used to calculate the dose compensating for prolonged time. Results: It revealed that, the relative percentage DNA in tail of cervical cancer cell line observed in comet assay were significantly decreased to 0.724 – 0.905 (p < 0.05) while relative surviving fraction increased to 1.02 – 1.17 to that of conventional technique. Although the surviving fraction tended to increase with increasing delivery time, only the surviving fraction at 30 min delivery time was statistical different. The absorbed dose of 204 cGy calculated by LQ model should be used to compensate for this impact. Conclusions: Prolonging treatment time allowed sublethal damage repair to take place during irradiation demonstrated by decreasing in DNA damage and subsequently increasing in cell survival. Therefore, biological effective dose should be compensated in advanced radiotherapy techniques which delivery time longer or close to repair half‐time of tumor cell.

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