Radioiodine thyroid remnant ablation in patients with differentiated thyroid carcinoma (DTC): prospective comparison of long-term outcomes of treatment with 30, 60 and 100 mCi

Abstract

BackgroundThe aim of this study is to compare the effectiveness of 131I therapy between three groups of DTC patients who received 30, 60 or 100 mCi for thyroid remnant ablation after total thyroidectomy and were postoperatively judged with low risk of cancer recurrence.MethodsThe project was designed as a two-stage, prospective randomized clinical trial. In 1998-2001 in a randomized prospective study the early comparison of treatment with 30 mCi vs 60 mCi suggested the lower 131I activity to be less effective, whereas in 2003-2005 the comparison between 60 vs 100 mCi showed no significant differences. The present study comprises the long-term assessment of the disease course in 3 study groups.ResultsA group of 309 DTC patients (285 women and 24 men) with no clinical, histopathological, sonographical or biochemical signs of persistent disease were included after total thyroidectomy and appropriate extent of neck lymph node dissection (265 with papillary and 44 with follicular thyroid cancer). For radioiodine thyroid remnant ablation, 30 mCi of 131I was applied in 86 patients, whereas 60 mCi in 128 and 100 mCi in 95 patients. The median follow-up was 10 years (2-12) for subjects treated with 30 mCi and 60 mCi and 6 years (2-6) for patients treated with 100 mCi of 131I. In the first evaluation, published previously, we observed that because of incomplete thyroid remnant ablation, the second 131I treatment was necessary in 10% patients, without difference between groups treated with 60 and 100 mCi and in 22% patients treated with 30 mCi. All patients entered full remission. To evaluate the long-term outcome of the adjuvant 131I treatment, the course of the follow-up and the most recent disease status were assessed by sonography, radiological examinations and serum Tg estimation (on LT4-suppressive treatment). Within the whole observation period local relapse was stated in 2 (2.4%), 4 (3%) and 3 (3%) patients treated with 131I activities of 30 mCi, 60 mCi and 100 mCi respectively and serum Tg concentration on LT4-suppressive treatment was low, without differences between groups.ConclusionsNo significant differences in the 5 years efficacy of thyroid remnant radioiodine ablation using 30, 60 and 100 mCi were observed in low-risk DTC patients operated by total thyroidectomy and neck lymph node dissection. However, patients treated initially with 30 mCi, required second course of radioiodine in 22%, while this was necessary only in 13,3% and 11,2% of patients treated with 60 mCi and 100 mCi respectively.

Rekomendacje Polskich Towarzystw Naukowych „Diagnostyka i leczenie raka tarczycy”. Aktualizacja na rok 2018

“…So far, there are no convincing data speaking in favour of one, defined dose. The most positive Polish experiences refer to RAI activities of 2.2-3.7 GBq (60-100 mCi) [57].…”

Completion thyroidectomy of well-differentiated thyroid cancer — a prospective, miserandomised study

“…According to the literature, the thyroid gland captures 1-1.75% of I 131 per gram of thyroid tissue. In cases of WTC, the uptake is lower than 0.5% per gram [23,26,27]. This may result in limited effectiveness of adjuvant radioiodine therapy and further legitimates the radical approach both in the primary and secondary surgical treatment.…”

“…[28][29][30]. Ablation therapy is not at all necessary when iodine uptake after 24 hours (T24 h) is less than 1-3% [25][26][27][28]. Iodine uptake > 1%/3% is an indication for adjuvant radioiodotherapy.…”

“…The statement of the European Thyroid Association (ETA) is more liberal and recommends ablative treatment after total thyroidectomy only in T3-4 stages of primary tumour or in cases of metastases to lymph nodes (N1). Experience in Poland suggests I 131 therapy also for pT 1b -T 2 ,N 0 ,M 0 cases [26,33].…”

Anaplastic thyroid cancer – an overview of genetic variations and treatment modalities

“…There have been several trials evaluating strategies to redifferentiate radioiodine-resistant well differentiated thyroid cancers in an attempt to render these tumors responsive to this treatment modality. 75,76 A recent study by Ho et al 77 successfully used selumetinib, a selective allosteric MEK1 and MEK2 inhibitor as a means to reestablish radioiodine avidity in non-iodine avid advanced papillary thyroid cancer. The activation of the MAPK or MEK is thought to play a critical role in the pathogenesis of radioiodine resistance.…”