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

Abstract

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.

High Failure Rates After 131I Therapy in Graves Hyperthyroidism Patients With Large Thyroid Volumes, High Iodine Uptake, and High Iodine Turnover

“…Often fixed activities of 370 or 555 MBq (10 or 15 mCi) are used, which will result in hypothyroidism in 69% to 90% of patients. 19,20,28,29 Similar results, however, are achieved with calculated activities, taking into account thyroid volume, the uptake of 131 I, and the quantity of activity to be deposited per milliliter (eg, activity (MBq) = gland volume (mL) Â 370 to 740 MBq/mL Â [1/24-hour uptake on % of dose]). Activities in the lower end of the spectrum lead to a higher proportion of treatment failure.…”

“…14Y18 Some centers have tried to obtain satisfactory results with standard activities of 131 I. 19,20 Others, like our institution, use a ''patient-tailored'' calculated dose by using a particular activity of radioiodine (3.7 or 7.4 MBq, respectively, 0.1 or 0.2 mCi) per milliliter of thyroid volume based on a formula first described by Marinelli et al 21,22 and also taking into account the thyroid volume in combination with 5-and 24-hour iodine turnover ratios. 23Y25 The goal of this study was to evaluate 131 I therapy outcome by identifying patient characteristics positively and independently associated with 131 I treatment failure in a large cohort of patients with Graves hyperthyroidism treated with either a calculated ''standard'' activity of 3.7 MBq/mL (0.1 mCi/mL) of thyroid volume or a ''double'' activity of 7.4 MBq/mL (0.2 mCi/mL) of thyroid volume.…”

Factors Predicting Treatment Failure in Patients Treated with Iodine-131 for Graves′ disease

“…Many studies addressing this topic have shown that empirical therapy is not inferior to dosimetry based therapy and higher dose (370 MBq) is associated with higher cure rates than lower doses (185 MBq). [141516] Moreover, aim of treatment of Grave's disease is to achieve either euthyroidism or hypothyroidism and so treatment with higher doses remains a logical choice with acceptable higher risk of hypothyroidism. [17] However, even with higher doses of up to 370 MBq dose a fraction of patients do not respond to a single dose of therapy.…”

Thyrotoxicosis and radioiodine therapy: Does the dose matter?

“…There is a lack of consensus towards what dose of radioiodine should be used and whether the aim of treatment is to render the patient euthyroid for a period of time or hypothyroid. [3–5] Some endocrinologists believe that sustained euthyroidism would clearly be the most desirable outcome but this would appear to be futile. A review from the 1980s stated unequivocally that the goal of radioactive iodine treatment in patients’ with Graves’ disease should be complete ablation of the gland.…”

“…As radioactive iodine therapy is relatively inexpensive, incurring further costs determining the dose of radioiodine that should be administered needs to be justified. [5]…”