Radioiodine ablation after thyroidectomy could be safely abandoned or postponed in selected stage I papillary thyroid carcinoma patients of low-risk group: an observational prospective study

Background. The European Thyroid Association consensus for the management of differentiated thyroid cancer (2006) suggested to avoid radioactive iodine (RAI) after thyroidectomy in patients with unifocal microcarcinoma (≤ 1 cm) with no extension beyond the thyroid capsule and without lymph node metastases. As the new data was collected and the risk stratification was revised, in 2022 the same recommendation was expanded to the patients with microcarcinoma and central neck lymph node involvement. The American Thyroid Association guidelines (2015) advocated no RAI ablation after hemi- or total thyroidectomy for thyroid cancer less than 1 cm with 5 and less micrometastases up to 2 mm in central neck lymph nodes as this strategy has no negative impact on the disease prognosis. In low-risk patients, no sufficient evidence of the obligatory postsurgical radioiodine ablation has been yet demonstrated. The aim of our study was to reveal whether RAI after thyroidectomy can be abandoned or postponed until the disease progression is confirmed in low-risk patients. Materials and methods. Two groups of patients (30 per group, 60 in total) with papillary microcarcinoma Т1N1a (5 and less level VI micrometastases up to 2 mm) were observed during a 5-year follow-up. In the first group, patients received 100 mCi (3.75 GBq) I131 shortly after total thyroidectomy while in the second group, postponed RAI was applied when progression signs were observed (elevated serum thyroglobulin level and US/CT suspected findings) after thyroid surgery. Results. After 5 years, no significant difference between groups was observed regarding post-RAI local recurrences (one in the first group and two in the second group) and/or distant metastases (t-test, p = 0.58). All cases of neck recurrences were treated with subsequent surgical excision, with no new data of progression within the specified follow-up. Conclusions. RAI adjuvant therapy for papillary thyroid carcinoma Т1N1a may not be necessary for patients with small number of level VI micrometastases. Local and distant metastases revealed during the careful follow-up by thyroglobulin level elevation and when using visualization techniques can be effectively treated with postponed RAI therapy and/or surgery.