Low-Dose Radioiodine Ablation in Patients with Low-Risk Differentiated Thyroid Cancer

Abstract

Aim: Based on the response criteria of the 2015 American Thyroid Associations guidelines, our objectives were to ­determine the response rate when using a low dose of ­131-I GBq in patients with low-risk differentiated thyroid cancer (LRDTC) and the influence of clinical and analytical variables on the prediction of complete response. Methods: We performed a multicentre and longitudinal study, including patients who were operated for LRDTC and who underwent radioiodine remnant ablation with a low-dose of 131-I. All patients were assessed at 6–12 months, and their status was classified as complete (excellent response) or incomplete response (structural incomplete, biochemical incomplete or indeterminate response). Various factors including age, gender, histology, tumour focality and size, stage, time from surgery to treatment, type of thyroid-stimulating hormone (TSH) stimulation, preablation serum thyroglobulin (pTg), antiTg antibodies (pAntiTgAb) and TSH (pTSH) levels were also analysed in order to predict the complete response rate. Results: Of 108 patients, 79.6% achieved complete response and the remaining showed incomplete response (2.9, 5.5 and 12% due to biochemical incomplete, structural incomplete and indeterminate response respectively). Six patients received a new dose of 131-I. Tumour size and pAntiTgAb were the only factors related to therapeutic response (p = 0.03 and p < 0.01, respectively). However, pAntiTgAb was the only independent factor related to complete ­response. Patients with complete response showed lower pTg than those with incomplete response (5.1 ± 12.9 vs. 11.2 ± 25 ng/mL) although without statistical significance (p = 0.14). There was no significant difference in the response rate depending on the thyrotropin stimulation methods. Conclusions: A low dose of 131-I was sufficient for reaching a complete response at 6–12 months of follow-up in the majority of patients with LRDTC. Tumour size and pAntiTgAb variables were related to therapeutic response.

Efficacy of Low-Dose Radioiodine Ablation in Low- and Intermediate-Risk Differentiated Thyroid Cancer: A Retrospective Comparative Analysis

“…The main difference of our study to HiLo was anti-TgAb consideration that was not described in this clinical trial, and with ESTIMABL1 the difference was the inclusion of intermediate-risk tumours. Nevertheless, the rate of excellent response in the low-dose group was 78.9%, and this result is comparable to previous studies [8,9,11,14,15].…”

“…In the HiLo study, they compared low-risk and intermediate-risk tumour recurrence rates with low (<100 mCi) and high doses (≥100 mCi) of RAI, showing a noninferior result (1-2% risk of recurrence at 5 years in both groups) [8]. Other authors, such as Ghachem [9], Schlumberger [14], Qi [15] or Jiménez-Londoño [11], have reported similar results in observational studies, concluding that low doses were noninferior to high doses in patients with low-risk thyroid cancer. In our study, we observed a higher rate of indeterminate responses in the group treated with low doses of RAI and a higher rate of excellent and incomplete biochemical responses in the group of high-dose ablation, with statistical significance.…”

“…Despite the results of ESTIMABL1 and HiLo suggesting that low-dose RAI ablation is effective in patients with low-and intermediate-risk thyroid cancer, and many subsequent papers supporting this idea [9][10][11], there is no international consensus on RAI dose. In fact, the European Association of Nuclear Medicine and the Society of Nuclear Medicine and Molecular Imaging refused to endorse the ATA 2015 guidelines.…”

Role of Emerging Environmental Risk Factors in Thyroid Cancer: A Brief Review

“…However, treatment of DTC with 131 I is still an open issue because recommendations of experts are based only on data interpretation of observational retrospective studies. The results of the prospective trials are pending, and the use of 131 I is justified in high-risk, intermediate-risk, and low-risk patients [71,72] according to the guidelines of the American and British Thyroid Association, European and American Societies of Nuclear Medicine, the European Consensus Group, and the latest edition of National Comprehensive Cancer Network (NCCN) [71,73].…”

Ablation therapy using a low dose of radioiodine may be sufficient in low- to intermediate-risk patients with follicular variant papillary thyroid carcinoma

“…8 Additionally, some authors have concluded that a low dose of radioiodine is as effective as a high dose of radioiodine for ablation of the thyroid remnant after total thyroidectomy for low-risk DTC. [33][34][35] Several factors are associated with unsuccessful RAI ablation, but in most studies, only lymph node recurrence was a significant factor. 36 In this research, in addition to lymph node recurrence, we found persistent positive Tg value and some false positive I-131 imaging, like thyroglossal duct cyst and thymoma uptaking I-131, all led to multiple RAI.…”