Use of a dosimetry-based RAI protocol for treatment of benign hyperthyroidism optimises response while minimising exposure to ionising radiation

BACKGROUND

The optimal treatment strategy for radioiodine (RAI) treatment protocols for benign hyperthyroidism remains elusive. Although individualised activities are recommended in European Law, many centres continue to provide fixed activities. Our institution implemented a dosimetry protocol in 2016 following years of fixed dosing which facilitates the calculation of individualised activities based on thyroid volume and radioiodine uptake.

METHODS

This was a retrospective study comparing success rates using a dosimetry protocol targeting an absorbed dose of 150 Gy for Graves' disease (GD) and 125 Gy for Toxic Multinodular Goiter (TMNG) with fixed dosing (200MBq for GD and 400MBq for TMNG) among 204 patients with hyperthyroidism. Success was defined as a non-hyperthyroid state at 1 year for both disease states. Results were analysed for disease specific or patient specific modulators of response.

RESULTS

This study included 204 patients; 74% (n = 151) received fixed activities and 26% (n = 53) of activities administered were calculated using dosimetry. A dosimetry-based protocol was successful in 80.5% of patients with GD and 100% of patients with TMNG. Differences in success rates and median activity administered between the fixed (204Mbq) and dosimetry (246MBq) cohort were not statistically significant (p = .64) however 44% of patients with GD and 70% of patients with TMNG received lower activities following treatment with dosimetry as opposed to fixed activities. Use of dosimetry resulted in successful treatment and reduced RAI exposure for 36% of patients with GD, 70% of patients with TMNG, and 44% of patients overall.

CONCLUSION

This retrospective clinical study demonstrated that treatment with a dosimetry-based protocol for TMNG and GD achieved comparable success rates to fixed protocols while reducing RAI exposure for over a third of patients with GD and most patients with TMNG. This study also highlighted that RAI can successfully treat hyperthyroidism for some patients with activities lower than commonplace in clinical practise. No patient or disease specific modulators of treatment response were established in this study; however, the data supports a future prospective trial which further scrutinises the individual patient factors governing treatment response to RAI.

Simultaneous hot and cold thyroid nodules: Which is malignant?

Physicians should be aware of the risk of malignancy in patients with toxic multinodular goiter. Radionuclide scan cannot be used to predict the malignant potential of thyroid nodules. A comprehensive evaluation of imaging studies is needed.

The Role of Nuclear Medicine in the Clinical Management of Benign Thyroid Disorders, Part 1: Hyperthyroidism

Benign thyroid disorders, especially hyper- and hypothyroidism, are the most prevalent endocrine disorders. The most common etiologies of hyperthyroidism are autoimmune hyperthyroidism (Graves disease, GD), toxic multinodular goiter (TMNG), and toxic thyroid adenoma (TA). Less common etiologies include destructive thyroiditis (e.g., amiodarone-induced thyroid dysfunction) and factitious hyperthyroidism. GD is caused by autoantibodies against the thyroid-stimulating hormone (TSH) receptor. TMNG and TA are caused by a somatic activating gain-of-function mutation. Typical laboratory findings in patients with hyperthyroidism are low TSH, elevated free-thyroxine and free-triiodothyronine levels, and TSH-receptor autoantibodies in patients with GD. Ultrasound imaging is used to determine the size and vascularity of the thyroid gland and the location, size, number, and characteristics of thyroid nodules. Combined with lab tests, these features constitute the first-line diagnostic approach to distinguishing different forms of hyperthyroidism. Thyroid scintigraphy with either radioiodine or ^99mTc-pertechnetate is useful to characterize different forms of hyperthyroidism and provides information for planning radioiodine therapy. There are specific scintigraphic patterns for GD, TMNG, TA, and destructive thyroiditis. Scintigraphy with ^99mTc-sestamibi allows differentiation of type 1 from type 2 amiodarone-induced hyperthyroidism. The radioiodine uptake test provides information for planning radioiodine therapy of hyperthyroidism. Hyperthyroidism can be treated with oral antithyroid drugs, surgical thyroidectomy, or ¹³¹I-iodide. Radioiodine therapy is generally considered after failure of treatment with antithyroid drugs, or when surgery is contraindicated or refused by the patient. In patients with TA or TMNG, the goal of radioiodine therapy is to achieve euthyroid status. In GD, the goal of radioiodine therapy is to induce hypothyroidism, a status that is readily treatable with oral thyroid hormone replacement therapy. Dosimetric estimates based on the thyroid volume to be treated and on radioiodine uptake should guide selection of the ¹³¹I-activity to be administered. Early side effects of radioiodine therapy (typically mild pain in the thyroid) can be handled by nonsteroidal antiinflammatory drugs. Delayed side effects after radioiodine therapy for hyperthyroidism are hypothyroidism and a minimal risk of radiation-induced malignancies.

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.

Hyperthyroidism

Hyperthyroidism is a condition where the thyroid gland produces and secretes inappropriately high amounts of thyroid hormone which can lead to thyrotoxicosis. The prevalence of hyperthyroidism in the United States is approximately 1.2%. There are many different causes of hyperthyroidism, and the most common causes include Graves' disease (GD), toxic multinodular goiter and toxic adenoma. The diagnosis can be made based on clinical findings and confirmed with biochemical tests and imaging techniques including ultrasound and radioactive iodine uptake scans. This condition impacts many different systems of the body including the integument, musculoskeletal, immune, ophthalmic, reproductive, gastrointestinal and cardiovascular systems. It is important to recognize common cardiovascular manifestations such as hypertension and tachycardia and to treat these patients with beta blockers. Early treatment of cardiovascular manifestations along with treatment of the hyperthyroidism can prevent significant cardiovascular events. Management options for hyperthyroidism include anti-thyroid medications, radioactive iodine, and surgery. Anti-thyroid medications are often used temporarily to treat thyrotoxicosis in preparation for more definitive treatment with radioactive iodine or surgery, but in select cases, patients can remain on antithyroid medications long-term. Radioactive iodine is a successful treatment for hyperthyroidism but should not be used in GD with ophthalmic manifestations. Recent studies have shown an increased concern for the development of secondary cancers as a result of radioactive iodine treatment. In the small percentage of patients who are not successfully treated with radioactive iodine, they can undergo re-treatment or surgery. Surgery includes a total thyroidectomy for GD and toxic multinodular goiters and a thyroid lobectomy for toxic adenomas. Surgery should be considered for those who have a concurrent cancer, in pregnancy, for compressive symptoms and in GD with ophthalmic manifestations. Surgery is cost effective with a high-volume surgeon. Preoperatively, patients should be on anti-thyroid medications to establish a euthyroid state and on beta blockers for any cardiovascular manifestations. Thyroid storm is a rare but life-threatening condition that can occur with thyrotoxicosis that must be treated with a multidisciplinary approach and ultimately, definitive treatment of the hyperthyroidism.

Treatment of Toxic Multinodular Goiter: Comparison of Radioiodine and Long-Term Methimazole Treatment

Background: This study aimed to compare the effectiveness and safety of long-term methimazole (MMI) and radioiodine (RAI) in the treatment of toxic multinodular goiter (TMNG). Methods: In this randomized, parallel-group trial, 130 consecutive and untreated patients with TMNG, aged <60 years, were enrolled and randomized to either long-term MMI or RAI treatment. Both groups of patients were followed for 60-100 months, with median durations of 72 and 84 months in the MMI and RAI groups, respectively. Results: In the MMI and RAI groups, 12 and 11 patients, respectively, were excluded because of side effects, choosing other modes of treatment and not returning for follow-up; 53 and 54 patients, respectively, completed the study for 60-100 months. In the MMI group, two patients (3.8%) experienced subclinical hypothyroidism, and 51 (96.2%) remained euthyroid until the end of study. The dosage of MMI to maintain euthyroidism was 6.3 ± 2.0, 4.5 ± 0.9, and 4.1 ± 1.0 mg daily during the first, third, and fifth years of continuous MMI treatment. One patient had elevated liver enzymes, and three developed skin reactions during the first three months, but no adverse effects from MMI occurred from 4 to 100 months of therapy. In the RAI group, 22 (41%) became hypothyroid, 12 (22%) had persistence or recurrence of hyperthyroidism, and 20 (37%) became euthyroid after 16.7 ± 2.7 mCi ¹³¹I. Conclusion: Long-term, low-dose MMI treatment for 60-100 months is a safe and effective method for treatment of TMNG, and is not inferior to RAI treatment.

Using plasma exchange to successfully manage thyrotoxicosis in a patient with possible antithyroid drug-related thrombotic thrombocytopenic purpura

OBJECTIVE

Thrombotic thrombocytopenic purpura (TTP) is a rare disease characterized by microangiopathic hemolytic anemia, thrombocytopenic purpura, neurologic abnormalities, fever, and renal insufficiency. The association or co-existence of thyrotoxicosis or antithyroid drugs with TTP has not been previously reported. Subject and Results. Herein, we present a 54-year-old female patient newly diagnosed with toxic multinodular goiter accompanying with TTP, possibly triggered by either thyrotoxicosis or antithyroid drugs.

CONCLUSIONS

The present report is the first in the literature to demonstrate the co-existence of these two diseases and the use of plasma exchange as a modality to treat both conditions.

Takotsubo Cardiomyopathy Associated with Primary Hyperthyroidism Secondary to Toxic Multinodular Goiter

Takotsubo cardiomyopathy is increasingly recognized as a distinct clinical entity. An association with thyroid disease has been identified in several case reports, mostly in the context of Grave disease. We report the case of a 67-year-old woman presenting with takotsubo cardiomyopathy and thyrotoxicosis secondary to toxic multinodular goiter. Previously unreported, this suggests that this association is related to the direct effects of thyroid hormone, rather than an autoimmune mechanism. Thyroid disease should be considered in patients presenting with takotsubo cardiomyopathy.

Reduction in relapse rate of radioiodine therapy in patients of toxic multinodular goiter: A quality improvement project

Introduction:

Radioiodine (I-131) therapy is the definitive treatment of toxic multinodular goiter (TMNG). Treatment failure may result in relapse after I-131 therapy. The present study was undertaken to reduce treatment failure rate of I-131 therapy in TMNG patients.

Materials and Methods:

Multiple causes may have lead to treatment failure of I-131 in TMNG patients making it difficult to establish a direct cause–effect relationship and take corrective action. Therefore, the JURAN methodology of quality improvement was applied. The treatment failure rate in 80 TMNG patients treated with I-131 in the period 2003–06 was 29%. The root cause analysis identified delay in decision to radioablate and concomitant antithyroid drugs (ATD) with I-131 therapy as factors leading to relapse. In 2007, a change in management was introduced with decision to radioablate all TMNG patients not remitting at 1 year of ATD and to withdraw ATD for 2 weeks prior to I-131 therapy. A total of 63 patients of TMNG followed the changed protocol between 2007 and 2009. Further analysis showed that one of the factors identified in the initial brainstorming (high iodide pool in the patient) had not been addressed in the protocol currently followed. The protocol was modified to include patient preparation and implemented after standardization.

Results:

The post-I-131 relapse rate in patients treated after implementation of the new protocol from 2007 to 2009 was 18% which further reduced to 16% in 2011 after modification of the protocol.

Conclusion:

The failure rate of I-131 therapy in TMNG reduced from 29% to 16% through standardization of the treatment procedure achieved by the use of Juran Methodology that helped to identify process-related defects.