Prospective Study Confirms that Radioiodine Remnant Ablation Is Not Necessary in Low-Risk Differentiated Thyroid Cancer.

patients with different risk of recurrence [5] . The benefits of postoperative 131 I differs between the following groups: • ATA High-Risk Category. Patients are defined to be at high risk if they have macroscopic extrathyroidal extension, incomplete tumor resection, distant metastases, and postoperative serum Tg suggestive of distant metastases, large-volume lymph node involvement (any metastatic lymph node ≥ 3 cm in largest dimension), and follicular thyroid cancer with extensive vascular invasion (>4 foci of vascular invasion or extracapsular vascular invasion). The published literature supports 131 I ablation for high-risk patients. • ATA Intermediate-Risk Category. This includes patients with lymph node metastases (clinical N1 or >5 pathologic N1 with all involved lymph nodes <3 cm in largest dimension), intrathyroidal papillary thyroid cancer with a primary tumor of 1–4 cm that is BRAF mutated (if known), and multifocal papillary microcarcinoma with extrathyroidal extension and BRAF mutated (if known). In these patients, the decision to administer 131 I should be individualized according to risk factors such as adverse thyroid cancer histology, lymph node disease outside the central neck, and advancing age. • ATA Low-Risk Category. This includes patients with intrathyroidal PTC without vascular invasion, with or without small-volume lymph node metastases (clinical N0 or ≤ 5 pathologic N1 micrometastases of a few millimeters in size), intrathyroidal encapsulated follicular variant of papillary thyroid cancer or intrathyroidal well-differentiated follicular cancer with capsular or minor vascular invasion (<4 vessels involved), and Differentiated thyroid carcinoma (DTC) accounts for more than 80% of all thyroid cancers. An increasing incidence of DTC over the last decades has been reported worldwide, and is mainly due to the discovery of small papillary carcinomas [1] with an excellent prognosis. Such favorable prognosis may be due to the biological properties of these tumors and/or the effectiveness of the primary therapy [2, 3] : near total thyroidectomy followed by radioactive iodine (RAI) remnant ablation with 131 I. The aim of postsurgical ablation of the thyroid remnant with RAI is to facilitate the early detection of recurrence based on serum thyroglobulin (Tg) measurement and RAI whole body scan. In addition, RAI ablation may represent an adjuvant therapy by cleaning persistent microscopic foci of cancer, which can be present in the thyroid remnant. While the first aim – remnant ablation – is related to follow-up in any patient regardless of his specific risk, the second one – adjuvant therapy – is advocated as a tool to reduce the rates of disease recurrence or cause-specific mortality [4] , and thus its use must be justified according to a real risk of recurrence. In the past, RAI ablation was indicated in almost every patient with a diagnosis of DTC. Nowadays, careful revision of patients’ outcome has introduced the concept or risk-based selection of patient candidates to RAI ablation. The individual risk depends on initial prognostic indicators obtained at surgery and on results of serum Tg measurements and neck ultrasonography obtained after surgery [5] . According to these parameters, the American Thyroid Association (ATA) has defined three groups of Published online: January 16, 2016