Fixed-Dose Radioactive Iodine Reduces Goiter Size and Alleviates Hyperthyroidism in Most Patients with Toxic Multinodular Goiter
2020; Mary Ann Liebert, Inc.; Volume: 32; Issue: 6 Linguagem: Inglês
10.1089/ct.2020;32.273-275
ISSN2329-972X
Autores Tópico(s)Thyroid and Parathyroid Surgery
ResumoClinical ThyroidologyVol. 32, No. 6 HyperthyroidismFree AccessFixed-Dose Radioactive Iodine Reduces Goiter Size and Alleviates Hyperthyroidism in Most Patients with Toxic Multinodular GoiterBenjamin J. GigliottiBenjamin J. GigliottiDivision of Endocrinology, Diabetes and Metabolism; Department of Medicine; University of Rochester School of Medicine & Dentistry; Rochester, New York, U.S.A.Search for more papers by this authorPublished Online:5 Jun 2020https://doi.org/10.1089/ct.2020;32.273-275AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions Back To Publication ShareShare onFacebookTwitterLinked InRedditEmail Review of: Roque C, Santos FS, Pilli T, Dalmazio G, Castagna MG, Pacini F 2020 Long-term effects of radioiodine in toxic multinodular goitre: Thyroid volume, function and autoimmunity. J Clin Endocrinol Metab. Epub 2020 Apr 22. PMID: 32320467.SUMMARYBackgroundToxic multinodular goiter (TMNG) results from autonomous thyroid hormone production by thyroid nodules and is the second most common cause of hyperthyroidism after Graves’ disease; it is particularly common in older patients and in regions of iodine deficiency. Thyroidectomy or radioactive iodine (RAI; I-131) are definitive therapies.RAI may be more appropriate for patients who are older, have a significant history of surgical contraindications or a history of neck surgery, lack other thyroid/parathyroid pathology requiring surgery, and have small goiters or lack compressive symptoms. RAI requires several months to ablate thyroid tissue and has a higher rate of recurrence, as compared with surgery. However, it is well tolerated, less expensive, less likely to cause hypothyroidism, and is not associated with operative risk (1). RAI may be given as a calculated or a fixed dose. There is a paucity of long-term data on patient outcome after fixed-dose RAI for patients with TMNG. This study (2) was performed to assess the effects of 15 mCi of I-131 on changes in thyroid volume, thyroid function, and autoimmunity during long-term follow up.MethodsThis retrospective population-based study from Siena, Italy, included 153 adults (116 women, 37 men) with TMNG treated with a fixed dose of 15 mCi I-131. The diagnosis of TMNG was made through serum thyroid function tests, thyroid ultrasound, and scintigraphy. All patients were pretreated with methimazole (withdrawn 20 days before RAI) and underwent pretreatment measurement of urine iodine excretion to rule out excess iodine exposure.The primary outcome was a change in thyroid volume (measured via sonography, calculated by the ellipsoid formula), as well as thyroid function and autoimmunity via measurement of thyroid-stimulating hormone (TSH), free T4, free T3, anti-thyroglobulin antibody (TgAb), antithyroid peroxidase antibody (TPOAb), and thyrotropin receptor antibodies (TSHRAb). Exclusion criteria included treatment with surgery or long-term use of antithyroid drugs, use of human recombinant-TSH stimulation, and a lack of biochemical or radiographic data before or after treatment.ResultsPatients who underwent thyroid volume assessment had a mean (±SD) follow-up of 6.2±2.9 years. At 1 year after RAI therapy, the mean volume reduction was 30±17.8% and did not correlate with baseline size. The magnitude of shrinkage progressively decreased over time. By years 3 to 6, a total of 60% of patients had reached a nadir, with a mean maximal reduction of 45% in the 1st year to 76.5% in the 11th. After the nadir, 22% had volume regain, but the growth in all cases remained below the baseline thyroid volume.Patients who underwent laboratory testing had a mean follow up of 5.7±2.6 years. At the end of follow-up, 61.6% of patients were euthyroid (40% at 6 months, 61% by 1 year), 11% had hyperthyroidism (6.2% subclinical, 4.8% overt that required methimazole), and 27.4% had hypothyroidism (24.7% subclinical, 2.7% overt that required levothyroxine). The overall cure rate was 89%, and 82% of patients who had subclinical hyperthyroidism at 6 months were euthyroid within 3 years. The mean time to hypothyroidism was 2.7±2.4 years; these patients had a smaller baseline thyroid volume and greater volume reductions after RAI. In those with detectable titers, serum TgAb and TPOAb levels initially increased following the RAI therapy before they subsequently declined. Serum TSHRAb titers did not change.There were minimal adverse effects from therapy.ConclusionsTreatment of TMNG with a fixed dose of I-131 (15 mCi) is well tolerated and effective in reducing thyroid size by ≥50%. Although regrowth occurred in 22% of patients, any increases in thyroid size were still lower than baseline gland volumes. Hyperthyroidism was cured in 89% over a mean follow-up period of 5 to 6 years; hypothyroidism developed in approximately a quarter of patients.COMMENTARYRAI is often used for TMNG and may be given as a calculated or a fixed dose. Calculated dosages are based on thyroid volume (imaging or occasionally palpation, which is semiquantitative) and/or uptake (scintigraphy); the latter is theoretically more accurate owing to the wide variability of goiter/nodule size and iodine avidity. Fixed doses are more convenient and less expensive, but the administered dose may not correlate with the delivered dose. There is no consensus on which dosing method is superior; studies that suggest superiority often vary widely in dose, which is problematic, since higher doses are more effective at alleviating hyperthyroidism, regardless of how the dose is determined (3). The literature on this topic is heterogeneous: TMNG is often included alongside other causes of hyperthyroidism, patient age is variable and may impact outcome, multiple treatment methods are used (surgery often predominates), disparate outcomes are studied (cure rate and/or rates of hypothyroidism and/or size change), and/or a wide I-131 dose range is delivered, whether fixed or calculated. Therefore, a major strength of this study is the homogeneity of the population, since all subjects have TMNG and were treated with a single fixed dose of I-131. Other strengths include the robust study sample (>100 patients) and long duration of follow-up (>3 years).The results of this study are largely in line with other smaller studies that used similar fixed doses (4,5). Compared to the one of the largest cohorts to date from the Mayo Clinic, which used higher semi-calculated dosages of I-131 (average, ~30 mCi) (6), the frequency and magnitude of goiter reduction was higher in this study, but the cure rates for the two studies were similar. Interestingly, despite the large variation in goiter size in this study (8–256 ml), the baseline size did not appear to influence volume reduction, which differs from other studies (7). It is worth noting that Italy, where this study was conducted, is a region of relative iodine deficiency (8), and thus, avidity for I-131 may be higher; it is unclear whether a fixed 15-mCi dose would be as effective in iodine-sufficient regions.The main limitation of the study is its retrospective nature. The exclusion criteria and requirement of a baseline and posttreatment ultrasound and biochemical testing was necessary to answer the study's questions, but they introduced selection bias by reducing the cohort from 500 patients to 153.RAI dosing protocols vary by region and institution, and choosing a fixed versus a calculated dose strategy remains mostly a matter of style, since both have pros and cons and literature to support their use. Overall, this study further adds to the literature spanning more than five decades on this topic, confirming that RAI is a safe and effective treatment for TMNG.References1. Ross DS, Burch HB, Cooper DS, Greenlee MC, Laurberg P, Maia AL, Rivkees SA, Samuels M, Sosa JA, Stan MN, Walter MA 2016 American Thyroid Association guidelines for diagnosis and management of hyperthyroidism and other causes of thyrotoxicosis. Thyroid 26:1343–1421. Link, Google Scholar2. Roque C, Santos FS, Pilli T, Dalmazio G, Castagna MG, Pacini F 2020 Long-term effects of radioiodine in toxic multinodular goitre: Thyroid volume, function and autoimmunity. J Clin Endocrinol Metab. Epub 2020 Apr 22. Crossref, Medline, Google Scholar3. Rokni H, Sadeghi R, Moossavi Z, Treglia G, Zakavi SR 2014 Efficacy of different protocols of radioiodine therapy for treatment of toxic nodular goiter: Systematic review and meta-analysis of the literature. Int J Endocrinol Metab 12:e14424. Crossref, Medline, Google Scholar4. Danaci M, Feek CM, Notghi A, Merrick MV, Padfield PL, Edwards CR 1988 131-I radioiodine therapy for hyperthyroidism in patients with Graves’ disease, uninodular goitre and multinodular goitre. N Z Med J 101:784–786. Medline, Google Scholar5. Adamali HI, Gibney J, O'Shea D, Casey M, McKenna TJ 2007 The occurrence of hypothyroidism following radioactive iodine treatment of toxic nodular goiter is related to the TSH level. Ir J Med Sci 176:199–203. Crossref, Medline, Google Scholar6. Porterfield JR Jr, Thompson GB, Farley DR, Grant CS, Richards ML 2008 Evidence-based management of toxic multinodular goiter (Plummer's disease). World J Surg 32:1278–1284. Crossref, Medline, Google Scholar7. Bonnema SJ, Bertelsen H, Mortensen J, Andersen PB, Knudsen DU, Bastholt L, Hegedus L 1999 The feasibility of high dose iodine 131 treatment as an alternative to surgery in patients with a very large goiter: Effect on thyroid function and size and pulmonary function. J Clin Endocrinol Metab 84:3636–3641. Crossref, Medline, Google Scholar8. Olivieri A, Di Cosmo C, De Angelis S, Da Cas R, Stacchini P, Pastorelli A, Vitti P 2017 The way forward in Italy for iodine. Minerva Med 108:159–168. Medline, Google ScholarFiguresReferencesRelatedDetails Volume 32Issue 6Jun 2020 InformationCopyright 2020 American Thyroid Association, Inc.To cite this article:Benjamin J. Gigliotti.Clinical Thyroidology.Jun 2020.273-275.http://doi.org/10.1089/ct.2020;32.273-275Published in Volume: 32 Issue 6: June 5, 2020PDF download
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