Endocrinol Metab.  2016 Mar;31(1):168-173. 10.3803/EnM.2016.31.1.168.

Comparison of Fixed versus Calculated Activity of Radioiodine for the Treatment of Graves Disease in Adults

• Canto AU
• Dominguez
• Jimeno CA
• Obaldo JM
• Ogbac RV

• KMID: 2169709
• DOI: http://doi.org/10.3803/EnM.2016.31.1.168

Abstract

BACKGROUND
Radioactive iodine as a treatment modality has been shown in several studies to be a safe and effective therapy for Graves disease. However, there is still no uniformity regarding optimal dosing method. The aim of this study is to compare the efficacy of calculated and fixed dosing of radioiodine for the treatment of Graves disease.
METHODS
A hundred twenty-two patients diagnosed with Graves disease were randomized to receive either fixed or calculated dose of radioiodine. Those randomized to fixed activity received either low fixed activity at 9.9 mCi for thyroid gland size <40 g or high fixed activity at 14.9 mCi for thyroid gland size 40 to 80 g, and those grouped to calculated activity received 160 µCi/g of thyroid tissue adjusted for 24 hours radioiodine uptake. Thyroid function tests (free thyroxine [T4] and thyroid stimulating hormone [TSH]) were monitored at 10, 16, and 24 weeks after radioactive iodine therapy. The primary outcome, treatment failure was defined as persistently elevated free T4 and low TSH.
RESULTS
Of the 122 patients randomized, 56 in the fixed dose group and 56 in the calculated dose group completed the follow-up. At the end of 6 months, the percentage of treatment failure was 37.50% in the calculated dose group versus 19.64% in the fixed dose group with a relative risk of 0.53 (95% confidence interval, 0.28 to 0.98) favoring the fixed dose group.
CONCLUSION
Fixed dose radioiodine has a significantly lower incidence of persistent hyperthyroidism at 6 months post-radioactive therapy.

Keyword

Graves disease; Radioactive iodine; Hyperthyroidism

MeSH Terms

Adult*
Follow-Up Studies
Graves Disease*
Humans
Hyperthyroidism
Incidence
Iodine
Thyroid Function Tests
Thyroid Gland
Thyrotropin
Thyroxine
Treatment Failure
Treatment Outcome
Iodine
Thyrotropin
Thyroxine

Reference

1. Leslie WD, Ward L, Salamon EA, Ludwig S, Rowe RC, Cowden EA. A randomized comparison of radioiodine doses in Graves' hyperthyroidism. J Clin Endocrinol Metab. 2003; 88:978–983.

2. de Rooij A, Vandenbroucke JP, Smit JW, Stokkel MP, Dekkers OM. Clinical outcomes after estimated versus calculated activity of radioiodine for the treatment of hyperthyroidism: systematic review and meta-analysis. Eur J Endocrinol. 2009; 161:771–777.

3. DeGroot LJ, Jameson JL. Endocrinology: adult and pediatric. 6th ed. Philadelphia: Saunders;2010. p. 3525.

4. Sisson JC, Avram AM, Rubello D, Gross MD. Radioiodine treatment of hyperthyroidism: fixed or calculated doses; intelligent design or science? Eur J Nucl Med Mol Imaging. 2007; 34:1129–1130.

5. Bahn Chair RS, Burch HB, Cooper DS, Garber JR, Greenlee MC, Klein I, et al. Hyperthyroidism and other causes of thyrotoxicosis: management guidelines of the American Thyroid Association and American Association of Clinical Endocrinologists. Thyroid. 2011; 21:593–646.

6. Miranda-Padua ML, Cunanan EC, Kho SA, Marcelo M, Torres JF, Monzon OP, et al. A randomized double-blind comparison of fixed versus calculated radioiodine dose in the treatment of Graves' hyperthyroidism. Philipp J Intern Med. 2014; 52:1–7.

7. Aniel-Quimpo J, Cruz F, Chua C. Low versus high dose Iodine-131 treatment of hyperthyroidism due to Graves' disease. Philipp J Intern Med. 1992; 30:155–158.

8. Damle N, Bal C, Kumar P, Reddy R, Virkar D. The predictive role of 24h RAIU with respect to the outcome of low fixed dose radioiodine therapy in patients with diffuse toxic goiter. Hormones (Athens). 2012; 11:451–457.

9. Walter MA, Christ-Crain M, Eckard B, Schindler C, Nitzsche EU, Muller-Brand J, et al. Radioiodine therapy in hyperthyroidism: inverse correlation of pretherapeutic iodine uptake level and post-therapeutic outcome. Eur J Clin Invest. 2004; 34:365–370.

10. Allahabadia A, Daykin J, Sheppard MC, Gough SC, Franklyn JA. Radioiodine treatment of hyperthyroidism-prognostic factors for outcome. J Clin Endocrinol Metab. 2001; 86:3611–3617.

11. Walter MA, Briel M, Christ-Crain M, Bonnema SJ, Connell J, Cooper DS, et al. Effects of antithyroid drugs on radioiodine treatment: systematic review and meta-analysis of randomised controlled trials. BMJ. 2007; 334:514.

12. Lewis A, Atkinson B, Bell P, Courtney H, McCance D, Mullan K, et al. Outcome of 131I therapy in hyperthyroidism using a 550MBq fixed dose regimen. Ulster Med J. 2013; 82:85–88.