Is There Any Need for Adjusting 131I Activity for the Treatment of High Turnover Graves’ Disease Compared to Normal Turnover Patients? Results from a Retrospective Cohort Study Validated by Propensity Score Analysis

Abstract

Purpose To compare 131 I-therapy outcomes in high turnover and normal turnover Graves' disease patients and predict optimal first 131 I activity for high turnover patients. Methods Retrospective cohort design (1:2) validated by propensity score analysis. Cohort 1, high turnover (2-h RAIU/24-h RAIU ≥ 1), n = 104, and cohort 2, normal turnover (ratio < 1), n = 208, patients were compared for post 131 I outcome. The cure was defined as a combined euthyroid and stable hypothyroid state following 131 I treatment. Logistic regression analysis was used for identifying prognostic factors. The propensity score was applied; 77 matched pairs (1:1 ratio) of high and normal turnover patients were selected as a validation set. Results First 131 I cure rates of 28% in high turnover and 66% in normal turnover groups (p = 0.001) were noted. The therapy cycles (median, 2 vs. 1) and cumulative 131 I activity (median, 15 vs. 7 mCi) were required to cure hyperthyroidism in cohort 1 and cohort 2, respectively. Age (> 44 years), higher grade of goitre, and 2-h RAIU (> 37%) were associated with 131 I therapy failure. The high turnover patients needed a factor of 1.5-2 times more 131 I activity to achieve a similar cure rate compared to the normal turnover patients. The first-dose cure rate was 31% vs. 60% by propensity score analysis (n = 154), no way different (28% vs.66%) from the whole group of 312 patients. Conclusion High turnover Graves' disease patients, if administered standard 131 I activity, the outcomes shall be poor. To improve the success rate, 131 I activity should be increased by 1.5 to 2 times in the high turnover patients.

Efficacy of I-131 Treatment Dosage for Hyperthyroidism With Current Institution Formula

“…Our results further strengthened the outcome of retrospective analysis by Kuanrakcharoen that indicated a 66.3% success rate of I-131 treatment at 1 year [51]. However, the current findings contradicted the results of a recent retrospective study by Arora et al that indicated a variable (i.e., 31-60%) success rate of RAI treatment [52].…”

The EANM guideline on radioiodine therapy of benign thyroid disease

“…Moreover it may be refined by estimating the thyroid gland size by palpation, morphological, or functional imaging (i.e., TUS or thyroid scintigraphy, respectively) (i.e., fixed administered activity per mass unit) [ 1 , 6 ]. In addition, Na[ 131 I]I thyroid gland maximum uptake and turnover should be empirically taken into account when therapeutic RAI activity is planned [ 88 ].…”