The Effects Of Surgery And The Dosage Of ¹³¹I On The Initial Ablation In Differentiated Thyroid Carcinoma

Objective: Differentiated thyroid carcinoma is a kind of common endocrine malignancy. The standard treatment for DTC includes surgery, radioiodine (for remnant ablation and/or therapy) and levothyroxine (L-T4) replacement therapy. After total or near-total thyroidectomy, there still remain some thyroid tissues, including some micro or occult lesions that only can be seen by the microscope. Therefore, it has important clinical value by using ¹³¹I to ablate the residual thyroid tissue. After a successful ablation and cutting off the source of serum thyroglobulin, by detecting the changes of Tg level, any recurrence and metastasis of the disease can be monitored. If the initial ablation failed, it would be more hard for the second ablation.There are many factors influenced the initial ablation. The current study focused on how to make the patients acquired best effectiveness in the thyroid ablation. This study analyzed the effects of surgery and the dosage of ¹³¹I on the initial ablation in differentiated thyroid carcinoma.Methods: This study collected 64 cases of DTC patients from June 2006 to December 2008 who acceptted treatment in the nuclear medicine department of our hospital. All the patiens were in good condition and underwent total or near-total thyroidectomy before ablation treatment. Female patients were non-menstrual phase, pregnancy and lactation.According to the thyroidectomy, the patients were divided into two groups: total thyroidectomy and near total thyroidectomy. All patients should be prohibited to use L-T4, variety drugs and food which is riched in iodine for 3 4 weeks. In order to avoid the possible"stunning effect", ¹³¹I-whole body scan wasn't done and only thyroid stimulating hormone and thyroglobulin before the ablation were detected. After administration, the patients should use methylprednisolone for 3 days, sufficient dosage of L-T4, vitamin C and drink enough water, urinate in time.The follow up was performed after 3～6 months of ablation. Before the evaluation, the patients should stop using L-T4 for 3～4 weeks and make sure TSH higher than normal level. Absence of visible uptake compared with background was regarded as the criterion for successful ablation. Statistical study were performed by using SPSS 16.0. It was considered to have statistical significance when P <0.05.RESULTS: In this study, 73.4% of the patiens (47 cases) acquired successful ablation. All the patients did not appear serious side effects, such as severe nausea and vomiting. Few patients had mild reactions: neck discomfort and/or sore throat.This study included 64 cases of patients with DTC, 49 cases of female and 15 cases of male (female: male=3.3:1). The age ranged from 16 to 72 years, and the average age is 42.3±13.5 years old. The successful rate is 74.3% in≥45 years and 72.4% in <45 years, respectively. 73.5% females and 73.3% males acquired successful ablation. The successful rate is 74.1% in Papillary Thyroid Carcinoma, 71.4% in Follicular Thyroid Carcinoma and 66.7% in mixed Thyroid Carcinoma respectively. There was no significant difference for age, gender, pathological type among the groups. It was considered these factors were not related to the successful rate of ablation.The successful rate was 86.1% in total thyroidectomy and 57.1% in near-total thyroidectomy, respectively. The difference between two groups was significant (P <0.05). The successful rate in the group without metastasis is 85.2% and 78.6% in those with lymph node metastasis, and there's no significant difference between two groups. But the successful rate in the group with distant metastasis is 22.2%.There's statistical significance among three groups (P <0.05). There was significant difference between the groups of≤4 months (78.8%) and >4 months (50%) (P <0.05) for interval time from operation to radioiodine ablation. There was also significant difference for the ablation rate between the groups of TSH≥30 mIU/ml (84.2%) and TSH <30 mIU/ml (57.7%) (P <0.05). It was considered those factors including surgery approach in patients with DTC, with or without distant metastasis, the interval time between the operation and radioiodine ablation (month), serum TSH level were relevant to the successful rate.Analysis showed that, between the groups of 2.96 GBq ¹³¹I in 24 cases of patients and 3.7 GBq ¹³¹I in 33 cases of patients, there was no significant difference for the successful rate. When using 2.96 GBq ¹³¹I to ablate the thyroid remnant, the successful rate for the group of total thyroidectomy was 92.3%, which was higher than the group of near-total thyroidectomy significantly(P <0.05).There was significant difference (P <0.05) between the groups of Tg <30 ng/ml (success rate of 86.1%) and Tg≥30 ng/ml(success rate of 57.1%). It was considered that Tg could predict the successful rate of initial radioiodine ablation.CONCLUSIONS: Thyroidectomy, ¹³¹I therapy and levothyroxine (L-T4) replacement therapy is the best comprehensive methods for differentiated thyroid carcinoma patients. The hot spots of the current study is the surgical approach and the dosage for thyroid ablation in the patients of DTC. This study showed that: DTC patients should choose the total thyroidectomy and ablate the remnant tissues with ¹³¹I as soon as the wound healing. In the patients with or without lymph node metastases, their ablation efficacy were similar between 2.96 GBq and 3.7 GBq. When using 2.96 GBq ¹³¹I to ablate the thyroid remnants, there's significantly difference for the successful rate of the groups with total and near-total thyroidectomy (P <0.05). The successful rate is higher in those patients with or without lymph node metastasis, shorter time from operation to the radioiodine ablation, and higher serum TSH level. Serum Tg <30 ng/ml could be a good predictor of first radioiodine ablation for post-surgical thyroid remnants treatment.