**5. Follow-up of patients with DTC**

Most differentiated thyroid cancers are characterized by an indolent course with low morbidity and mortality. The methods used in the long-term follow up of patients with DTC are clinical examination, US (with special focus on the thyroid bed and lymph node status of the neck), serum thyroglobulin measurement with anti-Tg-antibodies, 131I WBS and in selected cases CT, MRI and positron emission tomography (18F-FDG-PET).

• **Indeterminate response** constitutes nonspecific biochemical or structural findings. This includes patients with Tg between 0.2 and 1 ng/ml during suppressive therapy and stimulated Tg between 1 and 10 ng/mL or nonspecific imaging findings as US data of subcentimeter avascular thyroid bed nodules or atypical LNs, faint uptake in the thyroid bed on WBS [5]. If these nonspecific findings become suspicious during the follow-up or if Tg or anti-Tg antibody levels are rising, additional imaging or biopsy with cytology evaluation

Thyroid Cancer: Diagnosis, Treatment and Follow-Up http://dx.doi.org/10.5772/intechopen.77163 63

The initial LT4 treatment is reassessed during the long-term follow-up of DTC patients and

• For patients with a structural incomplete response to treatment during the follow-up, TSH level should be maintained ≤0.1 mU/L in the absence of contraindications [5]. The risk of therapeutically induced subclinical hyperthyroidism affects the cardiovascular system

• For patients with a biochemical incomplete treatment response, the serum TSH should be maintained between 0.1 and 0.5 mU/L, taking into account the initial ATA risk, Tg level, Tg

• For high-risk cancer patients who have an excellent (clinically and biochemically disease free) or indeterminate response to therapy, serum TSH may be maintained between 0.1 and 0.5 mU/L for up to 5 years after which the degree of TSH suppression can by reduced with

• Patients with excellent therapeutic response (clinically and biochemically disease free), patients with an initial low-risk and intermediate response and those who did not carry out remnant ablation may maintain their TSH in the lower half of the reference range (from 0.5

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

(rhythm disorders, atrial fibrillation) and the bones (osteopenia, osteoporosis) [62].

and wash-out Tg measurement in suspicious LNs are indicated [66].

the following **long-term serum TSH levels** are recommended:

dynamics over time and the risk of TSH suppression [5, 62].

continued surveillance for recurrence [5].

to provide adequate therapy to patients at high risk.

to 2 mU/L) [67].

**Conflict of interest**

I declare no conflict of interest.

**6. Conclusion**

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

18F-FDG-PET is indicated in the case of high-risk patients with elevated thyroglobulin and negative radioiodine WBS [65].

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

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

and/or


• **Indeterminate response** constitutes nonspecific biochemical or structural findings. This includes patients with Tg between 0.2 and 1 ng/ml during suppressive therapy and stimulated Tg between 1 and 10 ng/mL or nonspecific imaging findings as US data of subcentimeter avascular thyroid bed nodules or atypical LNs, faint uptake in the thyroid bed on WBS [5]. If these nonspecific findings become suspicious during the follow-up or if Tg or anti-Tg antibody levels are rising, additional imaging or biopsy with cytology evaluation and wash-out Tg measurement in suspicious LNs are indicated [66].

The initial LT4 treatment is reassessed during the long-term follow-up of DTC patients and the following **long-term serum TSH levels** are recommended:

