A clinical study on relationshipbetween iodine turnover rate and therapeutic efficacy of ¹³¹Itherapyin patients withGraves’ disease

Objectives: The purpose of this paper is to explore the relationship between iodine turnover rate and the therapeutic efficacy of ¹³¹I therapy and value of iodine turnover rate in adjustment of ¹³¹I treatment dose.

Methods: Retrospectively collected and analyzed Graves' disease person who had received ¹³¹I therapy in Nuclear Medicine Department of First Affiliated Hospital of China Medical University during September 2016 to December 2017. All patients had undergone iodine metabolic experiment in order to calculate iodine turnover rate, and then did follow-up study after receiving ¹³¹I treatment by outpatient service and telephone after therapy (follow-up time≧ 3 months ). After evaluation clinical outcome, patients were divided into 2 groups: cure group and unrecovered group. Based on iodine turnover rate, patients were divided into four groups: the first group iodine turnover rate ≤0.5, the second group 0.5< iodine turnover rate ≤0.7, the third group 0.7< iodine turnover rate ≤0.9, the fourth group iodine turnover rate >0.9, and analyzed the difference of the cure rate between four groups by Chi-square test. Compared iodine turnover rate and clinical characteristics date ( including age, gender, duration, serological indexes, 24h ¹³¹I uptake rate, history of ¹³¹I therapy, history of anti-thyroid drug treatment, thyroid weight, unit ¹³¹I treatment dose by thyroid tissue ) between cure group and unrecovered group by Mann-Whitney test, and then the factors with statistical differences were analyzed by logistic regression analysis.

Results: In this study, a total of 536 Graves' disease patients were collected, there were 125 (23.3%) male, 411 (76.7%) female, with mean age was 42.27 ± 13.49 years old. According to the evaluation standard of 2013 China Guidelines for Radioactive Iodine Therapy in Graves' disease, there were 306(57.09%) patients in cure group, and 230(42.91%) patients in unrecovered group. The cure rate of four group were 74.70% (62/83), 62.76% (150/239), 44.12% (75/170), 43.18% (19/44), respectively. Chi-square test showed that there were relationship between iodine turnover rate and cure rate (X² = 28.796, p < 0.001) in four groups. The Mann-Whitney test showed that, between cure group and unrecovered group, gender (Z = -0.075, P = 0.941), 24h ¹³¹I uptake rate (Z = 1.84, P = 0.066), history of ¹³¹I therapy (Z =- 0.268, P = 0.788) hadn't statistical differences, which there were statistically differences in age (Z = -3.15, P = 0.002), free triiodothyronine (FT₃) (Z = 3.17, P = 0.002), free thyroxine (FT₄) (Z = 2.11, P = 0.035), duration (Z = 2.59, P = 0.01), history of anti-thyroid drug treatment (Z = 2.53, P = 0.011), thyroid weight (Z = 8.57, P < 0.001), iodine turnover rate (Z = 5.98, P < 0.001), unit ¹³¹I treatment dose by thyroid tissue (Z = -6.05, P < 0.001). And then logistic regression analysis showed that thyroid weight (P < 0.001), iodine turnover rate (P < 0.001), unit ¹³¹I treatment dose by thyroid tissue (P = 0.022) are the independent influence factors of therapeutic efficacy of ¹³¹I therapy, and we get logistic regression equation : logit(P)=2.716-0.039*thyroid weight+0.233*unit ¹³¹I treatment dose by thyroid tissue-2.741*iodine turnover rate.

Conclusions: Iodine turnover rate is a independent influence factor of therapeutic efficacy of ¹³¹I therapy, which is a negative correlation, and the logistic regression equation can be used as a basis and reference for clinicians to make treatment decisions and adjust the treatment dose of ¹³¹I, so as to improve the cure rate of ¹³¹I therapy.