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 ¹³¹I-therapy outcomes in high turnover and normal turnover Graves' disease patients and predict optimal first ¹³¹I 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 ¹³¹I outcome. The cure was defined as a combined euthyroid and stable hypothyroid state following ¹³¹I 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 ¹³¹I 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 ¹³¹I 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 ¹³¹I therapy failure. The high turnover patients needed a factor of 1.5-2 times more ¹³¹I 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 ¹³¹I activity, the outcomes shall be poor. To improve the success rate, ¹³¹I activity should be increased by 1.5 to 2 times in the high turnover patients.

Supplementary information: The online version contains supplementary material available at 10.1007/s13139-020-00674-3.

Keywords: Graves’ disease; High turnover; Normal turnover; Radioiodine therapy; Turnover.

Fig. 1

Flowchart showing a selection of patient cohorts, follow-up, and outcome in high and normal turnover groups. Cohort 1 of 104 Graves’ disease patients with high turnover and cohort 2 as the control group (1:2 age/sex-matched normal turnover GD) were selected

Fig. 2

Time to event analysis (Kaplan Meier curves) (event: spontaneous conversion to hypothyroid state in euthyroid patients after completion of all RIT) showing the fate of euthyroid patients after completion of all RIT on long-term follow-up