Objective: To determine the efficacy and safety of cold iodine after radioactive iodine therapy (RAI) and the effects of prior antithyroid drug therapy in patients with Graves' disease.
Methods: We undertook a review of medical records of 280 consecutive patients with Graves' disease who were treated with RAI followed by cold iodine. Logistic regression methods were used to model treatment failure.
Results: Of the 280 patients, 246 (88%) were successfully treated with a single dose of RAI, whereas 34 patients (12%) required further therapy. The mean duration of time to achieve euthyroidism or hypothyroidism in successfully treated patients was 68 days. Of the 209 patients who were never given antithyroid drugs (ATDs), 190 (91%) were successfully treated with a single dose of RAI. No differences were found in patient age, thyroid gland size, or initial free thyroxine index between the successfully treated group and the treatment failure group among those who received RAI alone. Of the 71 patients who had been treated with ATDs before RAI administration, 56 (79%) were successfully treated with a single dose of RAI. The treatment failure rate of 21% in patients who had received ATDs was significantly higher than the 9% failure rate observed in those who were never given ATDs (P = 0.01). Multivariate analysis showed that larger gland size increased the likelihood of treatment failure [c2(2) = 11.76)] and prior treatment with ATDs doubled the risk of treatment failure after adjusting for gland size. No serious adverse events were noted after RAI or cold iodine therapy.
Conclusion: Treatment of Graves' disease with RAI followed by cold iodine was safe and effective. The use of ATDs before 131I ablation resulted in a 2.3-fold higher treatment failure rate. ATDs need be used only in high-risk persons, and if such therapy is undertaken, higher doses of 131I should be administered to reduce the incidence of treatment failure.