Cure Rates After a Single Dose of Radioactive Iodine to Treat Hyperthyroidism: The Fixed-Dose Regimen

Introduction Radioactive iodine (RAI) has been used to treat hyperthyroidism for more than 70 years. Cure rates after RAI therapy range between 80% and 100%, with some patients requiring two or more doses. There is continued debate over which dosing regimen is optimal. We evaluated our cure rates after giving a single dose of radioactive iodine to treat hyperthyroidism using the fixed-dose regimen as opposed to the calculated-dose regimen. Materials and methods We retrospectively reviewed the clinical records of patients who had received their first single dose of RAI between 2016 and 2021. The patients had clinical and biochemical assessments every six weeks until six months post-RAI therapy, then every three months thereafter, if still not cured. Patients were deemed cured if they developed persistent hypothyroidism or euthyroidism after a single dose of RAI. The data included baseline demographics, adverse events, and cure rates after RAI treatment. Results One hundred and thirty-eight patients received their first dose of RAI during the study period. Their mean ± standard deviation (SD) age was 56.9 ± 15.3 years, and there were 101 women and 37 men. The median duration of hyperthyroidism was 34 months, and 62% of the cases were affected by Graves' disease. A majority of patients (90%) were on an antithyroid drug prior to RAI therapy. The median (interquartile range) dose of RAI received by the group was 559 (546-577) megabecquerels (MBq). Four patients (2.9%) reported adverse events shortly after receiving RAI. Our overall cure rate was 87.7% amongst patients who received a single dose of RAI therapy. This number consisted of 96 patients (69.6%) who developed hypothyroidism and 25 patients (18.1%) who remained euthyroid. Our one-year cure rate was 84.1%. Further analysis revealed that women had a greater cure rate than men over the study period (92% vs 75.7%, p = 0.017).  Conclusion We have evaluated cure rates after a single dose of RAI therapy for the treatment of hyperthyroidism at our center. Our results are comparable to those reported at other centers using a similar dosing regimen.