Comparison of two fixed activities of radioiodine therapy (370 vs. 555 MBq) in patients with Graves' disease.

OBJECTIVE Radioiodine therapy is the most commonly used therapy for patients with Graves' disease (GD) in the United Kingdom. It is considered safe, effective and relatively inexpensive. The aim of our study was to examine the outcome of 131Iodine therapy in patients with GD when two different activities of 131Iodine were used. DESIGN A retrospective audit was undertaken to compare the efficacy of 370 (10 millicuries) versus 555MBq (15 millicuries) radioiodine therapy in patients with Graves' disease over a period of ten years. RESULTS Overall, 90% of the patients had a successful outcome from treatment with no significant difference in the success rate between the lower and higher activities or between genders. CONCLUSIONS 555 MBq of radioiodine was no more effective than 370 MBq in managing patients with Graves' disease. We therefore recommend that the higher activity should not be routinely used in these patients.