Association between iodine intake and treatment outcomes of radioiodine remnant ablation in patients with papillary thyroid cancer / 中华核医学与分子影像杂志

ABSTRACT

Objective To evaluate the association between iodine intake and treatment outcomes of radioiodine remnant ablation in patients with papillary thyroid cancer (PTC),and to investigate the determinants related to the ablation efficacy.Methods A total of 95 PTC patients (28 males,67 females;average age 39.8 years) without distant metastases from January 2013 to May 2014 were enrolled in this retrospective study.All patients underwent total thyroidectomy and 2-4 weeks of low iodine diet (LID) before initial 131I therapy.Patients were divided into 3 groups according to urinary iodine excretion (UIE):moderate-severe iodine deficiency group (0＜UIE＜50 μg/L,n =30),mild iodine deficiency group (50 μg/L≤UIE＜100 μg/L,n =26),adequate iodine group (100 μg/L ≤ UIE ＜ 300 μg/L,n =39).Patients were followed up for 3-6 months after radioiodine ablation,successful ablation was defined as no visible uptake in the thyroid bed on diagnostic 131I whole body scan and Tg level ＜2 μg/L (with negative TgAb),or no visible uptake in thyroid bed on posttreatment 131I whole body scan.x2 test,two-sample t test,Mann-Whitney u test and logistic regression analysis were performed.Results In all,84.2％ (80/95)of patients were successfully ablated.The successful rates in the three iodine intake groups were 96.7％ (29/30),84.6％ (22/26) and 74.4％ (29/39),respectively,with significant difference (x2=7.374,P＜0.05).Univariate analysis revealed that UIE,pre-treatment TSH,pre-treatment Tg and the amount of remnant thyroid tissue at ablation affected ablation efficacy (x2 =7.374,t =2.037,z =-2.966,x2 =4.144,all P＜0.05).Logistic regression showed that the level of pre-treatment Tg (P ＜ 0.05) and iodine intake (P ＜ 0.05) were independent factors of ablation efficacy.Conclusion Iodine intake before 131I remnant ablation is one of the important factors affecting treatment outcomes.Thyroid remnant could be more successfully ablated if reasonable LID protocols be adopted according to the iodine nutritional status before treatment.