**6. Conclusion**

neck), serum thyroglobulin measurement with anti-Tg-antibodies, 131I WBS and in selected

It is recommended that Tg is always assessed together with anti-Tg antibodies. In the presence of positive anti-Tg-antibodies, the interpretation of thyroglobulin is complicated [62, 63]. Often, this necessitates a WBS that can visualize recurrence in negative Tg (false negative due to the presence of anti-Tg-antibodies). In the positive for anti-Tg-antibodies' patients (e.g., PTC on the background of Hashimoto thyroiditis), the dynamic changes in serum levels of these antibodies may serve as an indirect marker for remission (decreasing titers of antibod-

18F-FDG-PET is indicated in the case of high-risk patients with elevated thyroglobulin and

Based on the clinical, laboratory and imaging results, a novel nomenclature was introduced in order to describe the status of the patient during follow-up, excellent response, biochemical incomplete response, structural incomplete response and indeterminate response to treatment [5]. Thus, the response to therapy determines the ongoing risk stratification, which

• **Excellent therapeutic response** or absence of persistent disease for patients who have undergone surgery and RAI ablation is defined by the presence of all following three

**a.** no RAI uptake outside the thyroid bed on the post-treatment or subsequent diagnostic

**3.** Low serum Tg during TSH suppression (Tg < 0.2 ng/mL) and after stimulation with thy-

• **Biochemical incomplete response** is characterized by abnormal thyroglobulin (Tg > 1 ng/ml during suppressive therapy and > 10 ng/mL after stimulation) in the absence of a localizable disease. If associated with stable or declining serum Tg values, a biochemical incomplete response should lead to continued observation with ongoing TSH suppression. Rising Tg or anti-Tg antibody values requires prompt additional imaging and potentially

• **Structural incomplete response is determined by persistence or new identification of loco-regional or distant metastases. The management (additional treatment or ongoing observation) depends on** the size, location, rate of growth, RAI avidity, 18F-FDG avidity

roxin withdrawal or rhTSH (Tg < 1 ng/mL) in the absence of anti-Tg antibodies.

cases CT, MRI and positron emission tomography (18F-FDG-PET).

further guides the long-term follow-up and the management decisions.

**b.** no US data for recurrence in thyroid bed or suspicious neck LNs

ies) or recurrence of the disease (rising titers) [64].

negative radioiodine WBS [65].

62 Thyroid Disorders

criteria (4, 5, 63):

WBS and/or

**1.** no clinical evidence of tumor; **2.** no imaging evidence of tumor

additional therapies [5, 16].

and specific pathology of the structural lesions [5].

The cornerstones of the preoperative diagnosis of thyroid cancer are the careful US examination, FNAB and cytology assessment of the suspicious thyroid nodules. An interdisciplinary team comprising endocrinologists, surgeons, pathologists, radiologists and oncologists should guide the patient through the diagnostic and treatment process. Strict criteria have been introduced for treatment options and follow-up on the base of initial and ongoing risk assessment in order to minimize the potential harm of over-treatment of low-risk patients and to provide adequate therapy to patients at high risk.
