Comparison of different 131 I doses for thyroid remnant ablation in patients with differentiated thyroid carcinoma

Abstract

Objective To compare the ablation efficacy of different 131I doses for thyroid remnant in patients with DTC,and to analyze the factors related to the ablation efficacy.Methods A total of 343 DTC patients without local or distant metastases post total or near-total thyroidectomy were enrolled into this study.The patients were divided into three groups according to the initial 131 I ablation dose:group A included 101 patients with 1850 to 2220 MBq,group B included 103 patients with 2590 to 2960 MBq,group C ineluded 139 patients with 3330 to 3700 MBq.The patients were followed up for 6 to 12 months after initial 131 I ablation.Successful ablation was determined according to follow-up 131 I whole body scan and TSH stimulated serum Tg levels ( ＜ 10 μg/L).The x2 test and logistic regression were performed.Results The overall successful rate was 63％ (215/343).The successful rates in groups A,B and C were 59％ (60/101 ),64％ (66/103) and 64％ (89/139),respectively,with no significant difference among three groups (x2 =0.657,P =0.720).Univariant analysis identified that gender ( P =0.030),type of surgery ( P ＜0.01 ),number of the operations (P =0.004),pre-treatment TSH ( P =0.019) and pre-treatment Tg ( P ＜0.01 ) levels were related to the successful ablation rate.Logistic regression identified type of surgery (P ＜0.01)and pre-treatment Tg (P ＜ 0.01 ) level as the independent predictors for successful ablation.Conclusions Low dose 131I for thyroid remnant ablation is almost similar to higher dose for DTC patients.However,the type of surgery and pre-treatment TSH stimulated Tg level affect the success rate of 131 I ablation. Key words: Thyroid neoplasms; Thyroidectomy; Iodine radioisotopes; Radiotherapy dosage