Analysis Of Influential Factors On The First ¹³¹I Ablative Therapy Of Postoperative Patients With Differentiated Thyroid Carcinoma And Evaluation Of The Environmental Radiation Safety

Objective:1.To make a comprehensive analysis of influential factors of the first large dose radioiodine-131(¹³¹I) ablative therapy of post-operative thyroid remnants in patients with differentiated thyroid carcinoma and to provide evidence for enhancing success rate.2.To analyze early adverse effects and safety of ablation therapy with large dose ¹³¹I.3.To monitor the level ofγ-ray's radiation of our ward after large dose of ¹³¹I therapy,to evaluate the safety of treatment process and identify the influence to the environment.Methods:1.46 post-operative DTC patients who received first large dose ¹³¹I ablative therapy were divided into two groups according to the results of ablation:ablation achieved group and ablation non-achieved group.Univariate analysis was carried out to analyze the influential factors such as ¹³¹I dose,age,sex,histological type,operation method,time from operation to radioiodine ablation,weigh of the residual thyroid, metastases,pathological stage etc.Based on the above date,we performed the multinomial logistic regression analysis to find the independent risk factors which had important effects on the ablation and to draw the receiver operator characteristic(ROC) curve.2.The results of blood routine test,liver function test.serum calcium,serum phosphonium and parathyroid hormone level between pre-ablation and post-ablation were investigated;the occurrence of radiotion thyroiditis(RT) and radiation sialoadenitis(RS) were analyzed.3.To analyze theγradiation levels which were detected with aγ-radiometer in our ward 24 hours after ¹³¹I therapy of 17 groups patients including one meter from the patients and different areas of our department.Results:1.Univariate analysis showed that the dose of ¹³¹I,the patients' age,sex, histological type,operation times,thyroid hormone replacement therapy before first ablation and pathological stage had no influence on the ablation result;while the operation method,weight of the residual thyroid,level of thyroid-stimulating hormone(TSH),time from last operation to the first radioiodine ablation and metastases were influential factors.Through analyzing the multiple influential factors we obtained the logistic regression equation of successful ablation:Y=3.766-0.947weigh of the residual thyroid-3.149lymph node metastases-3.373distant metastases.It demonstrated that low weight of the residual thyroid,no lymph node metastases,no distant metastases are protective factors to enhance the successful ablation rate.The area under ROC curve for weight of the residual thyroid was 0.871±0.054(P=0.000＜0.001),for metastases was 0.725±0.075(P=0.009＜0.01),which were effective to predict ablation successful rate.2.There were no statistical significance between pre-ablation and post-ablation results of blood routine test,liver function test,serum calcium,serum phosphonium and parathyroid hormone level.RT happened in five patients,incidence rate was 10.87%.RS happened in one patient,incidence rate was 2.17%.3.The maximumγradiation level was 21.71μSv/h in the ward,the staff can work 3.8 hours per day in this radiation environment according to the《Basic standards for protection against ionizing radiation and for the safety of radiation sources》of our country.The maximumγradiation level is 0.58μSv/h in the corridor of our department,the people can stay here for about 7.17 hours.Conclusions:1.There are many influential factors on the efficacy of the first ablative therapy in post-operative patients with DTC,low weight of the residual thyroid and no metastases are the protective factors to enhance the successful ablation rate.Total thyroidectomy should be performed to minimized the residual thyroid remnant and ¹³¹I therapy should be implemented as soon as possible after thyroidectomy.2.Large dose ¹³¹I ablative therapy is safe.There is little influence on the hematopoietic system, liver function and parathyroid function.RT and RS incidence rates are low.3.It is perfectly safe for our nuclear medicine staff to work in our ward after taking appropriate protective methods,since ionization radiation level in our ward is in the permitted range after ¹³¹I ablative therapy.Therefore the ionization radiation level in our department's environment is relative safety.