Prediction of post-treatment hypothyroidism using changes in thyroid volume after radioactive iodine therapy in adolescent patients with Graves' disease

Predictive factors for the outcome of radioiodine therapy in patients with benign thyroid diseases

PURPOSE

Radioiodine therapy (RIT) of benign thyroid diseases is an established therapy. This study aimed to identify factors predictive for outcome in patients with non-toxic goiter (NTG), unifocal (UFA), multifocal (MUFA) or diffuse autonomy (DISA) and Graves' disease (GD).

METHODS

Retrospective analysis of 205 patients with benign thyroid disease (54 NTG, 46 MUFA, 24 DISA, 26 UFA, 55 GD) who underwent RIT. Follow up time was 12 months for determining treatment outcome.

RESULTS

The type of disease was predictive for volume reduction after 12 months (NTS 66%, DISA 67%, MUFA 58%, UFA 51%, GD 71%, p<0.001) and post-treatment hypothyroidism (NTS 48%, DISA 33%, MUFA 15%, UFA 15%, p=0.006). Initial volume, intra-therapeutic uptake and intra-therapeutic half-life were independent prognostic factors for volume reduction 12 months after RIT. In patients with NTG, UFA, MUFA, DISA post-treatment hypothyroidism was significantly correlated with extent of volume reduction 12 months after RIT, achieved dose, higher pre-therapeutic TSH values and younger age. Two different strategies for pre-therapeutic dosimetry used in MUFA showed no differences regarding the therapeutic outcome. In GD, effective half-life, initial volume and Graves' ophthalmopathy were predictive for treatment failure.

CONCLUSION

Reduction of thyroid volume and the percentage of hypothyroid patients one year after RIT was primarily dependent on the type of disease. In MUFA and DISA we could identify volume reduction after 3 months as a reliable predictor for hypothyroidism while in patients with GD a short intra-therapeutic half-life, a large pre-therapeutic volume and active Graves' ophtalmopathy were relevant predictors for treatment failure suggesting an intensified follow-up scheme in these patients.

Long-term outcome of treatments for Graves disease in the children and adolescent population

BACKGROUND

Several studies were conducted over the years to find a significant association between non-surgical therapies such as Antithyroid Drug (ATD) Therapy and Radio-iodo therapy (RIT) with Graves' disease (GD) remission and relapse. However, these investigations did not have a specific focus on the age category of children and adolescents. Hence, this Research is performed to assess the association of non-surgical therapy (ATD and RIT) with Graves' disease (GD) remission and relapse in the children and adolescent population.

DESIGN

A systematic review and meta-analysis of observational studies and clinical trials were carried out.

METHODS

A systematic search of PubMed, EMBASE, and SCOPUS from their inception till April 2022 was performed for studies stating an association between ATD therapy and GD remission and relapse in participants 1-17 years old. The random-effects model was used in the meta-analysis to provide a pooled proportion of both primary outcomes. The quality and each study were assessed using the Newcastle Ottawa Scale (NOS).

RESULT

From 6195 studies searched from the databases, only 16 relevant articles remained after a detailed evaluation. These studies, having a total of 2557 patients aged 5-17 years, were involved in the analysis with a pooled estimate showing a significant association of ATD therapy with GD remission (Estimate: 0.400, 95% Confidence interval: 0.265-0.535; I^2 = 98.16%) and with GD relapse (Estimate: 0.359, 95% Confidence interval: 0.257-0.461; I^2 = 98.26%). Subgroup analyses were conducted to assess the remission rate of different therapies suggesting that antithyroid drugs play a significant role in the remission of the patients. All included studies were classified as moderate quality.

CONCLUSION

Following meta-analysis suggested that the ATD used in the analysis is effective in remitting GD in the children and adolescents population. Nevertheless, long-term RIT therapy and thyroidectomy leads to hypothyroidism. Still, large-sample, and high-quality studies targeting ATDs' use in children and adolescents with long-term surveillance of prognosis are needed.

The Efficacy and Short- and Long-Term Side Effects of Radioactive Iodine Treatment in Pediatric Graves' Disease: A Systematic Review

BACKGROUND

Graves's disease (GD) is the most common cause of hyperthyroidism. Maximal 30% of pediatric GD patients achieve remission with antithyroid drugs. The majority of patients therefore require definitive treatment. Both thyroidectomy and radioactive iodine (RAI) are often used as definitive treatment for GD. However, data on efficacy and short- and long-term side effects of RAI treatment for pediatric GD are relatively scarce.

METHODS

A systematic review of the literature (PubMed and Embase) was performed to identify studies reporting the efficacy or short- and long-term side effects of RAI treatment in pediatric GD.

RESULTS

Twenty-three studies evaluating 1,283 children and adolescents treated with RAI for GD were included. The treatment goal of RAI treatment changed over time, from trying to achieve euthyroidism in the past to aiming at complete thyroid destruction and subsequent hypothyroidism in the last 3 decades. The reported efficacy of a first RAI treatment when aiming at hypothyroidism ranged from 42.8 to 97.5%, depending on the activity administered. The efficacy seems to increase with higher RAI activities. When aiming at hypothyroidism, both short- and long-term side effects of treatment are very rare. Long-term side effects were mainly seen in patients in whom treatment aimed at achieving euthyroidism.

CONCLUSION

RAI is a safe definitive treatment option for pediatric GD when aiming at complete thyroid destruction. When aiming at hypothyroidism, the efficacy of treatment seems to increase with a higher RAI activity. Prospective studies are needed to determine the optimal RAI dosing regimen in pediatric GD.

Long-Term Outcomes of Radioiodine Therapy for Juvenile Graves Disease with Emphasis on Subsequently Detected Thyroid Nodules: A Single Institution Experience from Japan

OBJECTIVE

To investigate the long-term outcomes of radioiodine therapy (RIT) for juvenile Graves disease (GD) and the ultrasonographic changes of the thyroid gland.

METHODS

All of 117 juvenile patients (25 males and 92 females, aged 10 to 18 [median 16] years) who had undergone RIT for GD at our clinic between 1999 and 2018 were retrospectively reviewed. Each RIT session was delivered on an outpatient basis. The maximum 131I dose per treatment was 13.0 mCi, and the total 131I dose per patient was 3.6 to 29.8 mCi (median, 13.0 mCi). 131I administration was performed once in 89 patients, twice in 26, and three times in 2 patients. Ultrasonography of the thyroid gland was regularly performed after RIT. The duration of follow-up after the initial RIT ranged from 4 to 226 (median 95) months.

RESULTS

At the latest follow-up more than 12 months after RIT (n = 111), the patients' thyroid functions were overt hypothyroidism (91%), subclinical hypothyroidism (2%), normal (5%), or subclinical hyperthyroidism (2%). New thyroid nodules were detected in 9 patients, 4 to 17 years after initial RIT. Patients with newly detected thyroid nodules underwent RIT with lower doses of 131I and had larger residual thyroid volumes than those without nodules. None of the patients were diagnosed with thyroid cancer or other malignancies during the follow-up period.

CONCLUSION

Over a median follow-up period of 95 months (range, 4 to 226 months), RIT was found to be effective and safe in juvenile GD. However, cumulative evidence from further studies is required to confirm the long-term safety of RIT for juvenile GD.

ABBREVIATIONS

ATD = antithyroid drug; GD = Graves disease; KI = potassium iodide; LT4 = levothyroxine; MMI = methimazole; PTU = propylthiouracil; RAIU = radio-active iodine uptake; RIT = radioiodine therapy; 99mTc = technetium-99m; TSH = thyrotropin.

Long-term Effects of Radioiodine in Toxic Multinodular Goiter: Thyroid Volume, Function, and Autoimmunity

CONTEXT

Long-term studies evaluating the treatment of toxic multinodular goiter (TMNG) with fixed activities of radioiodine (RAI) are lacking.

OBJECTIVE

The objective of this work is to describe the effects of 15 mCi on thyroid volume, function, and autoimmunity in the long term.

DESIGN AND SETTING

A population-based, retrospective analysis with up to 12 years of follow-up was conducted in Siena, Italy.

PARTICIPANTS

Adult patients (n = 153) with TMNG, naive to RAI, were included.

METHODS

Evaluation was performed of thyroid function, antithyroid antibodies, and ultrasound scans before and yearly after RAI.

MAIN OUTCOME MEASURES

Evaluations included hyperthyroidism cure, hypothyroidism, volume reduction, nadir and regain, and antibody titer change.

RESULTS

The study revealed mean volume reductions greater than or equal to 50% at 3 years after RAI; the greatest annual reduction was observed during the first year (30 ± 17.8%; P < .001). Most patients (60%) achieved their volume nadir 3 to 6 years after RAI. Although 22% patients showed volume regain, the net reduction was statistically significant as late as 9 years after RAI (P = .005). The mean time to hypothyroidism was 2.7 ± 2.4 years, and it was associated with greater reductions in volume (P = .01). During the first 3 years after treatment, hyperthyroid patients decreased approximately by 50% per year without additional RAI. There was no statistically significant association of antibody titers with thyroid function except for antithyrotropin receptor antibodies and hyperthyroidism (P = .004). At the end of follow-up there were 61.6% euthyroid patients, 11% hyperthyroid (4.8% overt), and 27.4% hypothyroid patients (2.7% overt). Hyperthyroidism was cured in 89%.

CONCLUSIONS

The treatment of TMNG with 15 mCi of RAI induced low hypothyroidism rates while providing high cure rates and significant volume reduction, which was maintained in the long term.

Painful Radiation Thyroiditis after 131I Therapy for Graves' Hyperthyroidism: Clinical Features and Ultrasonographic Findings in Five Cases

BACKGROUND

Radiation thyroiditis caused by ¹³¹I therapy for Graves' hyperthyroidism is asymptomatic in most patients and is rarely associated with pain or fever. Currently, there are few reports on the ultrasonographic findings of radiation thyroiditis after ¹³¹I therapy for Graves' hyperthyroidism.

CASE REPORT

We herein report 5 cases with painful radiation thyroiditis (including 2 febrile cases) after ¹³¹I therapy for Graves' hyperthyroidism. The cases included 4 women, aged 49, 50, 76, and 81 years, and 1 man, aged 60 years. Anterior neck pain developed 0-10 days after ¹³¹I administration (fixed dose of 481 MBq). Each patient visited our clinic 0-4 days after the development of anterior neck pain. The thyroid glands were noticeably enlarged (increasing from 18 g at ¹³¹I administration to 35 g after the development of anterior neck pain in 1 patient, and from 20 to 33 g, 21 to 39 g, 21 to 51 g, and 40 to 51 g in the other patients) and tender. The echogenicity of the thyroid parenchyma was increased, and the parenchyma was more heterogeneous. Granular hyperechoic lesions were scattered throughout the thyroid gland in the most severe case. The border between the thyroid gland and the surrounding tissue was blurred, and the surrounding tissue was hyperechoic.

CONCLUSION

Painful radiation thyroiditis should be reacknowledged as one of the complications of ¹³¹I therapy for Graves' hyperthyroidism. Ultrasonography demonstrated the characteristic changes caused by ¹³¹I-induced radiation thyroiditis.

Radioiodine therapy for Graves disease: thyroid absorbed dose of 300 Gy-tuning the target for therapy planning

PURPOSES

Based on the committed thyroid absorbed dose, the aim was to compare the efficiency of I therapy against Graves disease (GD) within 1 year after treatment and, by exploring the dose-response relationship, indicate an absorbed dose to be targeted into patient therapeutic planning.

METHODS

Thyroid-absorbed doses were calculated to 196 patients with GD by applying Medical Internal Radiation Dose formalism and taking into account administered I activity, thyroid radioiodine uptake, effective half-life, and gland tissue mass. Statistical analysis was applied to assess the relationship between absorbed doses and the patient's clinical response.

RESULTS

Overall, successful therapy was achieved in 167 patients, whereas in 29 the disease persisted, even though 64.8% and 89.3% of all the treated patients had received, respectively, thyroid absorbed dose and activity superior to 300 Gy and 11.1 MBq/g (300 μCi/g) of thyroid tissue. Among those in whom the disease persisted, 24 (83%) had a 6- to 24-hour I uptake ratio equal or superior to 0.9, whereas only 5 (17%) presented a lower ratio. According to statistical analysis, there was no difference in cure rate between the groups that received 300 Gy or less and that which received more (84.1% vs 85.8%, P = 0.8336).

CONCLUSIONS

A thyroid absorbed dose of 300 Gy is plausible as a targeted therapeutic dose in GD therapy planning, because statistical analysis has proven there to be no advantage in treating patients with doses above this level. On the other hand, numerous efforts should be made to develop an optimized and easily applicable protocol of patient-specific dosimetry and to provide data that show its clinical impact on patient management.