Assessment of the Impact of Radioiodine Therapy of Thyroid Cancer in Postoperative Cases using Scintigraphy

Abstract

Iodine-131 has been used for over 60 years in the treatment of patients with DTC, to destroy both remaining thyroid cells and carcinoma foci. (Voutilainen PE, 2003). This study was carried out on 100 Saudi patients (20 male and 80 female) with ratio 1:2 whose ages ranged between (20-75) years old , mean age of patients were 42.8±12.6 years , the most age frequent lied between 31- 40 years during the period from June 2016 to February2018 at King Khalid Hospital –Najran .Pre therapy dxWBS was done 48 hrs after administration of I 131 (3mCi) to determine the ablation dose and RxWBS was performed 7 days after administration of iodine therapy dose (range 3.3-4.4 GBq) for detection and localization or exclusion of functioning thyroid remnants, persistent or recurrent local disease or distant metastasis in patients receiving I- 131 therapy. All patients came for follow –up after 6-12 months to assess the success of ablation and to identify which patients might require repeat RAIT, the success rate of ablation is determined by negative whole body 131 I scan. The most frequent histological type of thyroid carcinoma was papillary thyroid carcinoma. TSH level prior to I131 dose was >30mIU/L. The mean ablation dose was 100.80 ± 11.9 mCi ranged from 3.33 to 4.44 GBq (90 to 120 mCi) of 131I, with a median follow-up of 1 year (ranged 6months–18 months) with 185 MBq (5 mCi) of I 131. From the study group it was seen that follow-up WBS was positive scans (there were recurrences) in 4 (4.0%) patients, the majority 96 patients (96.0%) had negative scans (success of Ablation). The relation between whole body scintigraphy finding and age showed that the mean age in negative and positive scan were 43.06 years, 36.75 years respectively. Relation between histological type of thyroid carcinoma and age group the papillary thyroid carcinoma was more in age group (31-40) years. The correlation between histological type and gender showed that the most histological type of female IV and male was papillary thyroid carcinoma repeated 58 and 18 times respectively. The mean ablation dose was 100.83 in negative scan and 100.0 in positive scan. Regarding T stage in T1, 48 patients were negative scans and 3 patients were positive scans, in T2, 26patients were negative scans and there is no positive, in T3, 22 patients were negative scans and 1 was positive scan. In nodal stage the group with no lymph node invasion 96 patients were successfully ablated and 2patients with recurrence and group with lymph node involvement 2 patents with positive scans and there was no negative scan. There was no distant metastasis case in the study group. The mean tumor size was 2.69cm in negative scan and 2.50 cm in positive scan. The result showed that papillary thyroid carcinoma was highly responsive to radioiodine therapy. Comparing between RT lobe and LT lobe of thyroid gland the study showed that RT lobe of thyroid gland was more affected than LT lobe by a ratio of 3:2. Most of the patients in the study sample were successfully ablated.