Extremely high doses of radioiodine required for treatment of Graves' hyperthyroidism: a case report

Predictive factors for the outcomes of Graves' disease patients with radioactive iodine (131I) treatment

Although radioactive iodine (¹³¹I) treatment (RIT) is recommended as the preferred option for patients with Graves’ disease (GD), the predictive factors for its clinical outcomes are still unclear. In the present study, we aim to investigate the factors influencing the success rate of RIT treatment on primary GD with a calculated dose approach. The thyroid function (hyperthyroidism, euthyroidism or hypothyroidism) was evaluated at least 1 year after RIT, and its relationship with presenting clinical characteristics and pre-RIT parameters was analyzed in 45 patients retrospectively. After RIT, the remission rate was 62.2%, including 13 euthyroidism cases (28.9%) and 15 hypothyroidism cases (33.3%). We found no significant association between the types of thyroid function and age, gender, the 3-h radioactive iodine uptake (RAIU) prior to RIT, or radioactive iodine (¹³¹I) dosage. However, a variable 24-h RAIU > 46.31% was found associated with the success rate of RIT. The present study implied that a calculated dose approach for GD is effective, but high failure rates are expected in patients presenting poor 24-h RAIU, particularly those with 24-h RAIU below 46.31%.

Predictive factors of outcomes in personalized radioactive iodine ((131)I) treatment for Graves' disease

BACKGROUND

Graves' disease (GD) is the most common cause of hyperthyroidism in iodine-sufficient areas. Radioactive iodine I treatment (RIT), as the 1st therapeutic option, is widely accepted by doctors and patients. The aim of this study was to investigate factors influencing the success rate of calculated RIT in GD.

METHODS

Thyroid function outcome (hyperthyroidism or euthyroidism/hypothyroidism) was verified retrospectively at least 1 year after RIT and was compared with presenting clinical characteristics and pre-RIT parameters in 167 patients with GD treated with I-iodide in the authors' institute.

RESULTS

After RIT, 83 patients (49.7%) became euthyroid, 64 patients (38.3%) became hypothyroid and 20 (12.0%) remained hyperthyroid. Multiple logistic regression analyses demonstrated that there was no statistically significant association between RIT outcomes and sex, age, history of GD, previous antithyroid drug treatment, thyroid hormone levels, thyroid gland mass or radioactive iodine I dosage. The only variables associated with the success rate were the course of disease over 6 months (odds ratio, 3.70; confidence interval, 1.75-7.17; P = 0.014) and 2-hour radioactive iodine uptake (RAIU) >58.5% (odds ratio, 4.08; confidence interval, 2.03-7.83; P = 0.005).

CONCLUSIONS

Our study has shown that a calculated approach for the treatment of GD was effective, but high failure rates were observed in patients presenting higher 2-hour RAIU, particularly those with 2-hour RAIU of more than 58.5%.

Evidence for higher success rates and successful treatment earlier in Graves' disease with higher radioactive iodine doses

BACKGROUND

Graves' disease is commonly treated with curative intent using radioactive iodine (RAI). While higher doses have been shown to increase success rates, more evidence is needed. Further, very few studies assess the time to treatment success without the need for antithyroid drugs after a single dose of RAI within the first year post-dose, despite earlier success being an important treatment objective. We aimed to evaluate the outcome of different RAI doses in terms of success rates and time to achieve this success (eu- or hypothyroidism). We hypothesized that higher doses would not only increase success rates, but bring about successful treatment earlier.

METHODS

We retrospectively analyzed the medical records of all patients diagnosed with Graves' disease between 1994 and 2009. Details of RAI treatment and outcomes thereof were documented. In our analysis, we divided the patients who received RAI treatment into three groups according to the dose received: I (≤15 mCi); II (16-20 mCi); III (≥21 mCi).

RESULTS

There were 498 patients diagnosed with Graves' disease. However, 105 were either lost to follow-up or still undergoing treatment. Of the remaining 393, there were 258 who received RAI treatment. The average initial dose was 21.42±6.5 mCi and overall success rate was 86%. Success rates were 74%, 85%, and 89% (p<0.05), while average time to successful treatment was 8.1, 4.6, and 2.9 months, respectively (p<0.001), for groups I, II, and III. When 20 mCi was given empirically, 85% obtained successful treatment; most of these within 3 months (mean 3.9; mode and median 3 months).

CONCLUSIONS

This study provides additional evidence that success post-treatment correlates with administered dose and shows clearly, for the first time, that successful treatment is achieved earlier with higher doses. This knowledge is relevant to all clinicians managing Graves' disease as it can be taken into consideration when discussing treatment plans with patients.