Dosimetry-guided radioiodine therapy of hyperthyroidism: long-term experience and implications for guidelines

Abstract

Background Long-term follow-up after radioactive iodine therapy (RIT) for Graves’ disease and toxic thyroid autonomy is incompletely addressed by current guidelines. We retrospectively analyzed the clinical course of 1233 out of 1728 consecutive Graves’ disease (n = 536) and thyroid autonomy (n = 1192) patients after dosimetry-guided RIT to optimize follow-up. Methods Patients were referred between 1990 and 2018; follow-up was monitored according to available electronic registers with medical reports, including autopsies from 9 hospitals and 10 residential care homes. Results In total, 495/1728 cases were censored because of incomplete 6-month follow-up data. The conversion rates to hypothyroidism in Graves’ disease and different forms of thyroid autonomy can be deconvoluted into two follow-up periods: first year after RIT and afterward. The conversion rate in Graves’ disease was significantly higher than that in all thyroid autonomy subgroups during the first year but almost identical afterwards. Thyroxine substitution started between 10 and 7900 days after RIT at thyroid stimulating hormone between 0.11 and 177 µU/ml. Conclusions We advise earlier (2–3 weeks) first follow-up checks after RIT in all Graves’ disease patients and thyroid autonomy under antithyroid drugs (ATD) and re-checks every 2–4 weeks until conversion to hypothyroidism during the first year. The first check in thyroid autonomy without ATD should be after 3–4 weeks with re-checks every 4–6 weeks. After 1 year, both groups can be re-checked every 4–6 months over the next 5 years. The success rate of RIT in thyroid autonomyincreases with age but the history of RIT is rapidly lost during follow-up.

Analysis of NIS Plasma Membrane Interactors Discloses Key Regulation by a SRC/RAC1/PAK1/PIP5K/EZRIN Pathway with Potential Implications for Radioiodine Re-Sensitization Therapy in Thyroid Cancer

“…The NIS expression at the PM of thyroid follicular cells is not only important for thyroid hormone biosynthesis but also constitutes the cornerstone for radioiodine (RAI) therapy for differentiated thyroid cancer (DTC) [4][5][6]. Indeed, the selective use of RAI, based on patients' individual risk, is often recommended as an adjuvant treatment for DTC, for which the standard care includes total thyroidectomy and TSH-suppressive therapy.…”

SFE-AFCE-SFMN 2022 Consensus on the management of thyroid nodules : What is the role of functional imaging and isotopic treatment?

“…Few studies compared efficacy and safety between these methods in this indication. Only one randomized study in patients with autonomous nodules showed equivalent efficacy with lower risk of hypothyroidism for calculated than fixed radioactivity methods [26], [28], [29], [30]. However, although more complex to implement, dosimetric methods should ideally be preferred, as internal vectored radiotherapy should be performed with "the lowest effective activity possible" (ALARA principle: As Low As Reasonably Achievable).…”

“…The speed of regression of hyperthyroidism depends on factors influencing iodine uptake, and correlates with radioactivity level [29]. The risk of secondary hypothyroidism persists for up to 20 years after RAI therapy, with cumulative rates of approximately 7% at 6 months to 30% at 20 years [28], [32]. The risk of hypothyroidism correlates with patient age, radioactivity level, TSH value at the time of therapy, and pre-existing underlying thyroid disease (presence of antithyroid antibodies before RAI therapy) [27], [28], [31].…”

“…The risk of secondary hypothyroidism persists for up to 20 years after RAI therapy, with cumulative rates of approximately 7% at 6 months to 30% at 20 years [28], [32]. The risk of hypothyroidism correlates with patient age, radioactivity level, TSH value at the time of therapy, and pre-existing underlying thyroid disease (presence of antithyroid antibodies before RAI therapy) [27], [28], [31]. This risk of long-term hypothyroidism justifies regular longterm biological monitoring, with annual TSH assay.…”