Real-world Data on Intermediate-risk Differentiated Thyroid Cancer Biochemical Response to 3700 or 5550 MBq of [131I]Sodium Iodide.

Abstract

Introduction: The ideal [¹³¹I]Sodium Iodide activity for intermediate-risk thyroid cancer treatment is still uncertain. The objective of this study is to compare the biochemical responses to radioiodine therapy (RIT) of intermediate-risk thyroid cancer patients administered [¹³¹I]Sodium Iodide at doses of 3700 MBq (100 mCi) and 5550 MBq (150 mCi).

Methods: A retrospective study was conducted by reviewing the medical records of intermediaterisk thyroid cancer patients who received RIT between 2016 and 2020 at a reference cancer hospital in Brazil. Sociodemographic and clinical data were evaluated at the time of diagnosis. Clinical data during two years of follow-up were reviewed, and biochemical responses were determined according to the American Thyroid Association (ATA, 2015 version). Responses to doses of 3700 MBq (100 mCi) and 5550 MBq (150 mCi) of [¹³¹I]Sodium Iodide were compared.

Results: No significant statistical differences were observed concerning the biochemical therapeutic responses of patients treated with 3700 MBq or 5550 MBq (p = 0.088). The presence of nodal metastasis and positive pre-RIT thyroglobulin did not influence biochemical responses to radioiodine.

Discussion: According to ATA 2015 guidelines, RIT may be administered to patients classified at intermediate risk for the ablation of post-surgical tissue remnants, as well as an adjuvant treatment for potential persistent tumor foci and to reduce recurrence risks. These recommendations, however, do not specify the appropriate radioiodine dosage and this has been a topic of extensive debate.

Conclusion: Intermediate risk thyroid-cancer patients presented similar therapeutic responses to the doses of 3700 MBq and 5550 MBq [¹³¹I]Sodium Iodide.