Success rate of radioiodine therapy in Graves' disease: the influence of thyrostatic medication

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%.

Predictors of euthyreosis in hyperthyroid patients treated with radioiodine 131I-: a retrospective study

BACKGROUND

Radioiodine (RAI) treatment for hyperthyroidism is a very common modality, chosen by physicians worldwide. The outcome of the therapy, however, is not always predictable. While rendering a patient hypo- or euthyroid is meant as a therapeutic success, the latter does not require lifelong hormonal supplementation. The aim of our study is to determine predictors of euthyreosis in patients who underwent RAI treatment.

METHODS

Medical records of 144 patients who had undergone RAI therapy were examined. Laboratory and clinical data were analyzed statistically. Ultrasonography findings, such as thyroid volume, nodules' size and characteristics had been collected at the beginning of treatment and 6 months after the administration of radioiodine ¹³¹I^-. Moreover, scintigraphy results were taken into account. Multivariate logistic regression analysis model has been used to find predictors of euthyroidism after 12 months of follow-up. The predictors of normal thyroid function have also been analyzed separately for patients with GD (Graves' disease) and TMNG (toxic multinodular goiter).

RESULTS

The analysis showed that age (OR 1,06; 95%CI 1.025-1.096, p = 0,001), thyroid gland volume (OR 1,04; 95%CI 1,02-1,06; p < 0.001) and iodine uptake level (OR 0,952; 95%CI 0,91-0,98; p = 0,004) were significant factors of achieving normal thyroid function after RAI therapy. According to multivariate logistic regression analysis, in GD patients only age has been shown to be a significant factor (OR 1,06; 95%CI 1,001-1,13; p = 0.047), while in TMNG patients' age (OR 1,04; 95%CI 1-1,09; p = 0.048), thyroid gland volume (OR 1.038; 95%CI 1.009-1.068; p = 0.009) and iodine uptake level (OR 0.95; 95%CI 0.9-0.99; p = 0.02) all have been proven to be significant predictors of achieving euthyroidism.

CONCLUSIONS

The more advanced age, larger volume of thyroid gland and lower iodine uptake level are predictors of euthyreosis after RAI treatment.

Prognostic factor analysis in 325 patients with Graves' disease treated with radioiodine therapy

Introduction

¹³¹I therapy is a choice for Graves’ hyperthyroidism. Several factors that affect the success of ¹³¹I treatment in Graves’ disease (GD) patients have been put forward. The aim of this retrospective study was to evaluate the factors influencing the success of ¹³¹I therapy and the occurrence of hypothyroidism after ¹³¹I therapy.

Patients and methods

We reviewed 325 GD patients, who were well documented out of 779 cases, treated with ¹³¹I in the First Affiliated Hospital of Xi’an Jiaotong University between 2010 and 2016. We collected the potential influencing factors, including demographic data (age, sex, family history), iodine intake state, antithyroid drugs (ATD) taking, thyroid texture, complications of hyperthyroidism, physical and laboratory examinations [thyroid weight, effective ¹³¹I half-life time (T_eff), 24-h iodine uptake rate, tri-iodothyronine, thyroxine, free tri-iodothyronine (FT3), free thyroxine, thyroid-stimulating hormone, thyroglobulin antibody, thyroid microsome antibody, thyrotropin receptor antibody], and final administered dosages according to Quimby formula. The correlations between the prognosis of GD patients and these factors were analyzed by logistic regression analysis.

Results

Out of 325 patients, 247 (76.00%) were treated successfully with radioiodine. GD patients who were cured by ¹³¹I therapy were more likely to have smaller thyroid [odds ratio (OR)=0.988, 95% confidence interval (CI)=0.980–0.996, P=0.002], lower FT4 levels (OR=0.993, 95% CI=0.988–0.997, P=0.002), and shorter time of ATD withdrawal before ¹³¹I treatment (OR=0.985, 95% CI=0.975–0.996, P=0.002). Hypothyroidism occurred in 132 (41.00%) out of 325 patients. There was an increased risk of early hypothyroidism in patients with lower 24-h iodine uptake (OR=0.964, 95% CI=0.941–0.988, P=0.004), and treated with a lower total dose of iodine (OR=0.892, 95% CI=0.824–0.965, P=0.005) and a higher iodine dose per garm of thyroid tissue (OR=5.414E+14, 95% CI=45.495–6.444E+27, P=0.027).

Conclusion

Our results showed that ¹³¹I treatment was more successful in patients with lower weight of the thyroid, lower free thyroxine level, and shorter ATD taking period. Furthermore, early hypothyroidism after radioiodine treatment was more likely to occur in patients with lower 24-h iodine uptake, lower total dose of iodine, and higher iodine dose per garm of thyroid tissue.

The Influence of Antithyroid Drug Discontinuation to the Therapeutic Efficacy of (131)I in Hyperthyroidism

The influence of antithyroid drugs (ATDs) on the therapeutic efficacy of radioactive iodine in hyperthyroidism is still controversial. The aim of this study was to evaluate the effect of ATD discontinuation to the therapeutic efficacy of I-131 in hyperthyroidism patients with long-term ATD treatment. Retrospective study was done to 39 subjects with hyperthyroidism who had been treated with doses of 300 MBq radioactive iodine. The subjects were divided into three groups: Group I (n = 14) had been using ATDs for more than one year and discontinued more than three days; group II (n = 14) had been using ATDs for more than one year but discontinued only for three days or less, and group III (n = 11) has never been used any ATD before radioactive iodine treatment. There was a significant difference in the therapeutic efficacy after three months of radioactive iodine treatment between group I and group II (P = 0.018), group II and group III (P = 0.017), but not between group I and group III (P = 1.0). There was no observed difference on the therapeutic efficacy between the three groups at 6 months after radioactive iodine therapy (P = 0.143). Administration of ATDs more than 1 year without discontinuation decreased response of radioactive iodine treatment in 3 months follow-up. Discontinuation of ATDs for more than 3 days before radioactive iodine treatment is recommended.

The Incidence of Hypothyroidism Following the Radioactive Iodine Treatment of Graves' Disease and the Predictive Factors Influencing its Development

The purpose of this study is to evaluate and compare the incidence of hypothyroidism following different fixed radioactive iodine-131 (¹³¹I) activities in the treatment of Graves’ disease (GD) and to investigate the predictive factors that may influence its occurrence. This retrospective analysis was performed on 272 patients with GD who were treated with ¹³¹I, among whom 125 received 370 MBq and 147 received 555 MBq. The outcome was categorized as hypothyroidism, euthyroidism, and persistent hyperthyroidism. Multiple logistic regression analysis was performed to identify significant risk factors that affect the development of hypothyroidism. The incidence of hypothyroidism following the first low activity was 24.8% with a high treatment failure rate of 58.4%, compared with 48.3% and 32% following high activity. The overall cumulative incidence of hypothyroidism following repeated activities was 50.7%, out of which 73.9% occurred after the first activity and 20.3% after the second activity. The higher ¹³¹I activity (P < 0.001) and average and mild enlargement of the thyroid gland (P = 0.004) were identified as significant independent factors that increase the rate of incidence of hypothyroidism (Odds ratios were 2.95 and 2.59). No correlation was found between the development of hypothyroidism and the factors such as age, gender, presence of exophthalmos, previous antithyroid medications, and the durations, and Technetium-99m (Tc-99m) pertechnetate thyroid uptake. In view of the high treatment failure rate after first low activity and lower post high activity hypothyroid incidence, high activity is recommended for GD patients, reserving the use of 370MBq for patients with average sized and mildly enlarged goiter; this increases patient convenience by avoiding multiple activities to achieve cure and long-term follow-up.

The effect of prior antithyroid drug use on delaying remission in high uptake Graves' disease following radioiodine ablation

Antithyroid drugs (ATDs) have been shown to attenuate the effectiveness of radioiodine (radioiodine ablation, RIA) therapy in Graves' disease. We undertook a study to look at the impact of iodine uptakes on the outcome of (131)I therapy. To determine the effect of prior ATD use on the duration of time to achieve cure in patients with high vs intermediate uptake Graves' disease who received a fixed dose (15 mCi) of (131)I radioiodine. In a retrospective study of patients with Graves' disease, 475 patients who underwent RIA were followed-up on a two-monthly basis with thyroid function tests. Of the 123 patients with a documented preablation RAIU and consistent follow-up it was observed that 40 patients had an intermediate RAIU (10-30%) and 83 subjects had a distinctly increased uptake (>30%). Successful cure was defined as the elimination of thyrotoxicosis in the form of low free thyroxin and rising TSH levels. When a standard dose of 15 mCi (131)I was administered, a cure rate of 93% was achieved. The median duration of time to cure (TC) was 129 days. Surprisingly, a direct proportional linear relationship (R(2)=0.92) was established between time to cure and radioiodine uptake (TC> 3 0%=172days, TC10 - 3 0%=105 days, P<0.001). Patients who used ATD medications took a proportionately longer duration to achieve remission (TCNO ATD=102days, TCATD=253days, P<0.001). The effect of prior ATD therapy in delaying remission was amplified in the subset of patients with higher uptakes (TC> 3 0% + ATD=310days, TC> 3 0% + NO ATD=102days, P<0.001) compared to those with the intermediate uptakes (TC10 - 3 0% + ATD=126 days, TC10 - 3 0% + NO ATD=99 days, P<0.001). RIA, using a dose of 15 mCi achieved a high cure rate. Higher uptakes predicted longer time to achieve remission, with prior ATD use amplifying this effect.

Long-term carbimazole pretreatment reduces the efficacy of radioiodine therapy

INTRODUCTION

Data from several studies suggest that pretreatment with antithyroid drugs (ATD) before (131)I increases the risk of treatment failure. This effect has been demonstrated more consistently with propylthiouracil than with carbimazole (CMZ) or methimazole (MMI). Men with Graves' disease (GD) have a lower rate of remission with (131)I compared to women and the impact of long-term ATD pretreatment on the success of (131)I is unknown. The objective of our study was to compare the efficacy of fixed doses of radioiodine between patients with and without long-term CMZ pretreatment.

MATERIALS AND METHODS

We performed a retrospective study on 335 male patients with GD treated with (131)I from 1998 to 2008. 148 patients had been pretreated with CMZ, and the remaining 187 patients received (131)I without pretreatment. We compared the success rate of a single dose of (131)I, between patients with and without long-term CMZ pretreatment.

RESULTS

The success rate of a single dose of (131)I was significantly higher in patients without pretreatment than in patients who were pretreated with CMZ (91.4% vs. 82.3%, P = 0.01). The rate of hypothyroidism in the first 6 months after (131)I therapy was significantly higher in patients without pretreatment (55.1% vs. 44.6%, P = 0.05). There was also a trend for higher cumulative rate of hypothyroidism at last follow-up in nonpretreated patients (78.1% vs. 69.7%).

CONCLUSION

Male patients with Graves' hyperthyroidism pretreated with CMZ have lower efficacy with 131I therapy compared to nonpretreated patients. CMZ pretreatment given for a prolonged period reduces the efficacy of (131)I therapy.

Effects of antithyroid drugs on radioiodine treatment: systematic review and meta-analysis of randomised controlled trials

OBJECTIVE

To determine the effect of adjunctive antithyroid drugs on the risk of treatment failure, hypothyroidism, and adverse events after radioiodine treatment.

DESIGN

Meta-analysis.

DATA SOURCES

Electronic databases (Cochrane central register of controlled trials, Medline, Embase) searched to August 2006 and contact with experts. Review methods Three reviewers independently assessed trial eligibility and quality. Pooled relative risks for treatment failure and hypothyroidism after radioiodine treatment with and without adjunctive antithyroid drugs were calculated with a random effects model.

RESULTS

We identified 14 relevant randomised controlled trials with a total of 1306 participants. Adjunctive antithyroid medication was associated with an increased risk of treatment failure (relative risk 1.28, 95% confidence interval 1.07 to 1.52; P=0.006) and a reduced risk for hypothyroidism (0.68, 0.53 to 0.87; P=0.006) after radioiodine treatment. We found no difference in summary estimates for the different antithyroid drugs or for whether antithyroid drugs were given before or after radioiodine treatment.

CONCLUSIONS

Antithyroid drugs potentially increase rates of failure and reduce rates of hypothyroidism if they are given in the week before or after radioiodine treatment, respectively.

A mathematical model of optimized radioiodine-131 therapy of Graves' hyperthyroidism

BACKGROUND: The current status of radioiodine-131 (RaI) dosimetry for Graves' hyperthyroidism is not clear. Recurrent hyperthyroidism and iatrogenic hypothyroidism are two problems which interact such that trying to solve one leads to exacerbation of the other. Optimized RaI therapy has therefore begun to be defined just in terms of early hypothyroidism (ablative therapy) as physicians have given up on reducing hypothyroidism. METHODS: Optimized therapy is evaluated both in terms of the greatest separation of cure rate from hypothyroidism rate (non-ablative therapy) or in terms of early hypothyroidism (ablative therapy) by mathematical modeling of outcome after radioiodine and critically discussing the three common methods of RaI dosing for Graves' disease. RESULTS: Cure follows a logarithmic relationship to activity administered or absorbed dose, while hypothyroidism follows a linear relationship. The effect of including or omitting factors in the calculation of the administered I-131 activity such as the measured thyroid uptake and effective half-life of RaI or giving extra compensation for gland size is discussed. CONCLUSIONS: Very little benefit can be gained by employing complicated methods of RaI dose selection for non-ablative therapy since the standard activity model shows the best potential for cure and prolonged euthyroidism. For ablative therapy, a standard MBq/g dosing provides the best outcome in terms of cure and early hypothyroidism.