**4. Risk stratification**

Accurate staging and assessment of DTC risk are essential for its management, which determines the prognosis and guides therapeutic decisions and the intensity of surveillance [4]. Risk stratification in DTC was based on clinic-pathological features after a few weeks of completing thyroidectomy, which previously referred to a static estimate of disease-specific mortality. Nowadays, risk stratification is a dynamic, active process used to predict the appropriateness of minimalistic initial therapy, risk of recurrence, disease-specific mortality, and the most likely response to initial treatment, as shown in **Table 2**. Moreover, an excellent histopathology report is essential for proper risk stratification [1, 11]. The estimated risk of recurrence ranges from <1% to 55%, and it is classified as low if ≤ 5%, intermediate if 6%–20%, and high if >20%, based on the presence or absence of aggressive features, presence of local or distant metastases, and imaging features on whole-body post-therapy scans [1, 2, 11]

Several systems are designed for risk stratification, considering patients' age, tumor size, resection completeness, local invasion, and distant metastasis [12]. The DTC risk stratification is applied in the clinical setting despite a validated system's absence [12, 33]. The original ATA risk category design (low, intermediate, high) is usually applied in clinical practice with promising results [12]. However, the 2015

*DOI: http://dx.doi.org/10.5772/intechopen.108481 Aspects Considered in Differentiated Thyroid Cancer for Radioiodine Therapy*

ATA risk stratification system was built on retrospective studies where nearly all patients were treated with RAI. ATA risk stratification schema for selecting patients for adjuvant treatment is not conclusively validated. However, it prompts the physician to consider the various clinic-pathologic factors in managing low- intermediaterisk patients where the indication for RAI therapy may not be straightforward [1]. The initial risk stratification is revised during follow-up to evaluate the disease and treatment responses (dynamic risk stratification) because the biological behavior of the disease as a response to therapy was not accounted for in initial staging [11, 12].
