Endocrinol Metab (Seoul). 2022;37(3):524-532.

Clinical Outcomes of Repeated Radioactive Iodine Therapy for Graves' Disease.

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제1저자 김민주 · 교신저자 조선욱

PMID 35709827 PMC9262691 DOI 10.3803/EnM.2022.1418 IF 5.1 내분비대사내과

소속 (7)

Department of Internal Medicine, Seoul National University Hospital, Seoul, Korea.
Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
Seoul National University Hospital Healthcare System Gangnam Center, Seoul, Korea.
Department of Internal Medicine, Veterans Health Service Medical Center, Seoul, Korea.
Department of Internal Medicine, Kangwon National University School of Medicine, Chuncheon, Korea.
Department of Molecular Medicine and Biopharmaceutical Sciences, Graduate School of Convergence Science and Technology, Seoul National University, Seoul, Korea.
Thyroid Center, Chung-Ang University Hospital, Seoul, Korea.

Abstract

BACKGRUOUND Radioactive iodine (RAI) therapy is a successful therapeutic modality for Graves' disease. However, RAI therapy can fail, and RAI therapy after antithyroid drugs (ATDs) has a lower remission rate. Therefore, many patients require repeated RAI therapy. This study investigated the clinical outcomes of repeated RAI therapy for Graves' disease.

METHODS Patients who underwent RAI therapy as second-line therapy after failure of ATD treatment between 2001 and 2015 were reviewed. Remission was defined as hypothyroid or euthyroid status without ATD, and with or without levothyroxine at 12 months after RAI therapy.

RESULTS The 1-year remission rate after 2nd RAI therapy (66%, 152/230) is significantly higher than that after 1st RAI therapy (48%, 393/815) or long-term ATD treatment after 1st RAI therapy failure (42%). The clinical response to 2nd RAI therapy was more rapid. The median time intervals from the 2nd RAI therapy to ATD discontinuation (1.3 months) and to the start of levothyroxine replacement (2.5 months) were significantly shorter than those for the 1st RAI therapy. A smaller goiter size, a longer time interval between the 1st and 2nd RAI therapies, and a longer ATD discontinuation period predicted remission after the 2nd RAI therapy. Finally, in 78 patients who failed the 2nd RAI therapy, the mean ATD dosage significantly reduced 5.1 mg over 12 months.

CONCLUSION Repeated RAI therapy can be a good therapeutic option, especially in patients with smaller goiters and those who are more responsive to the 1st RAI therapy.

Keywords

Graves diseaseHyperthyroidismIodine radioisotopesIodine-131

Figures

**Fig. 1.** Clinical outcomes of radioactive iodine (RAI) therapy in Graves’ disease patients with antithyroid drug (ATD) failure. (A) Response for RAI therapy. (B) Cumulative remission rate within 1 year after each RAI therapy.

**Fig. 2.** Kaplan-Meier curves for antithyroid drug (ATD) discontinuation (A), and the start of levothyroxine (LT4) replacement (B) after each round of radioactive iodine (RAI) therapy among patients who achieved remission after the 1st RAI therapy (n=393) and 2nd RAI therapy (n=152).

**Fig. 3.** Change of antithyroid drug (ATD) dosage after radioactive iodine (RAI) therapy. (A) Change of ATD dosage in patients with persistent disease after each RAI therapy. (B) Patients who had persistent disease after 1st RAI therapy and received long-term ATD therapy were divided into two groups according to the 2nd RAI therapy, the 2nd RAI⁽⁺⁾ and 2nd RAI⁽⁻⁾ group. ATD dosage between two groups were compared, and ATD dosage in the 2nd RAI⁽⁺⁾ group was significantly higher than that in the 2nd RAI⁽⁻⁾ group between 3 and 12 months after 1st RAI therapy. ^aP<0.05 vs 2nd RAI⁽⁻⁾ group at each time.

그림 출처: PubMed Central 공개 논문 (PMC9262691)

Conflict of interest statement

CONFLICTS OF INTEREST . No potential conflict of interest relevant to this article was reported.

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