Outcome of I-131 therapy for Basedow's disease under anti-thyroid drug treatment

Objectives Anti-thyroid drugs (ATDs) are commonly discontinued for several days before I-131 therapy for Basedow's disease to obtain sufficient I-131 uptake to the thyroid. However, interruption of ATD administration may be harmful because of possible deterioration of symptoms especially in old patients. Therefore, it would be favorable if I-131 therapy would work under the ATD treatment.

Methods This study included 58 patients who underwent I-131 therapy for Basedow’s disease between January, 2006 and December, 2009. Fifty patients were performed I-131 therapy after discontinuation of ATDs (Group A) and 7 patients were administrated I-131 under the ATD treatment (Group B). Increased radioiodine uptake was confirmed with I-123 tracer study before I-131 administration in all patients. Therapeutic success was determined to be the induction of euthyroid or hypothyroid states without the ATD treatment. Success rates were assessed at 6 and 12 months after I-131 therapy.

Results Therapeutic success rates in Group A and Group B were 94% (47/50) and 43% (3/7) at 6 months and 98% (48/50) and 86% (6/7) at 12 months, respectively. There was no significant difference in estimated radiation doses to the thyroid in two groups, which were 292.8 ± 169.8 Gy in Group A and 223.6 ± 124.8 Gy in Group B.

Conclusions Although time to achieve therapeutic responses would be delayed when patients would undergo I-131 therapy under the ATD treatment, this method would be beneficial to patients in order to prevent symptomatic deterioration by the discontinuation of ATD treatment