Background/Objective: The optimal period of a low-iodine diet during preparation for radioactive iodine therapy (RAI) is not well established.At the University of Washington, we conducted a retrospective analysis of patients with a diagnosis of differentiated thyroid cancers who underwent total thyroidectomy and RAI during the period 2022-2024 and compared urine iodine concentration in patients who had either one-or two-week of low iodine diet (LID) prior to RAI.Case Report: All analyses were performed using SAS software 9.4 (SAS Institute, Cary, NC).There were 72 patients who met the criteria.The median age of this cohort was 46 years old (range:19-82) and 63.9% were female.Of these, 53 patients underwent a 1-week and 19 patients underwent a 2-week LID before RAI.The median value of urine iodine after a 2 weekrestriction was lower at 0.228 mol/L (29 mcg/L) (range: <0.079-1.481mol/L; <10-188 mcg/L) compared to 1 week at 0.362 mol/L (46 mcg/L) (range: <0.079-30.43 mol/L; <10-3863 mcg/L), but not statistically significant (p=0.24).Discussion: Although the urine iodine level was lower in 2 weeks restriction, there was no statistically significant difference between one versus two-week iodine restrictions following RAI.This suggests that a one-week LID may be adequate for RAI treatment.This would decrease time to treatment for patients and decrease the burden of LID.Conclusion: There is a need for future large prospective randomized control trials to identify the optimal duration of LID and determine the goal urinary iodine level for successful RAI ablation.
Tran et al. (Sun,) studied this question.