Differentiated Thyroid Cancer: Optimization of Patient Well-being, Treatment and Prognosis

Thyroid cancer is the most common endocrine malignancy with approximately 700 new cases in The Netherlands in 2018. Differentiated thyroid cancer (DTC), comprising both papillary (PTC) and follicular thyroid cancer (FTC), is the most frequent (80-85%) form of thyroid cancer. The studies presented in this thesis aimed at the prognosis and prognostic factors, and the long-term impact of treatment of patients with DTC, and using DTC patients, thyroid hormone metabolites (THM) in different thyroid states including their association with Quality of Life (QoL) were investigated.
The two major existing systems (2015 American Thyroid Association (ATA) Guidelines), AJCC/TNM staging system 8th edition) that have been designed to predict recurrence and survival in patients with DTC were evaluated, and results show that both system perform well. Subsequently, suggestions to improve the AJCC/TNM staging system by staging PTC and FTC differentially including different age cutoffs, and the ATA Risk Stratification System by adding age as a risk factor were given. Thereafter, it was shown that treatment of patients with DTC has a long-term impact on both QoL and ovarian reserve. Finally, it seems that THM 1) have no or negligible thyroidal origin, but are produced by peripheral metabolism of T4, and 2) are not an explanation of persistent symptoms in patients with hypothyroidism.