Optimizing care for patients with differentiated thyroid cancer

Differentiated thyroid cancer (DTC) is the most common endocrine malignancy. Survival rates are excellent, but recurrences occur in 5-20 percent of the patients. DIAGNOSIS Fine needle aspiration is the cornerstone for diagnosing cancer. Unfortunately, a considerable percentage of FNA specimen are indeterminate and do not predict the nature of the thyroid nodule. These non-diagnostic aspirates delay definitive diagnosis and cause patient anxiety. Chapter two focused on identifying factors associated with the adequacy rate of fine needle aspiration cytology. Ultrasound guidance is proposed to reduce the number of inadequate specimen. The rate of non-diagnostic FNA specimen was high in our hospital and ultrasound guidance was implemented, but it did not improve results. FOLLOW-UP The goal of follow-up is accurate surveillance for recurrent disease. Thyroglobulin (Tg) is a hormone produced exclusively by thyroid tissue and therefore used a tumor marker, especially for patients treated by total thyroidectomy followed by remnant ablation. However, in the presence of thyroglobulin-antibodies (Tg-Ab), the Tg values can be falsely lowered of elevated. Chapter 3 focused on the postsurgical follow-up of patients with DTC. Patients with undetectable Tg one year after initial treatment had a very low recurrence rate, this also applied to high-risk patients. The negative predictive value of undetectable serum Tg one year after surgical and postoperative radioactive ablation treatment is very high (97%). We argue that a dynamic classification system is more appropriate; also using response to therapy to classify DTC patients. In Chapter 4 we studied the hypothesis that Tg-Ab can be used as a surrogate tumor marker. In our cohort, the risk of recurrence was negligible for patients with declining or stable Tg-Ab level in patients with an undectectable Tg level. In case of rising Tg-Ab levels, the treating physician should actively try to diagnose recurrent disease. In the majority of patients however, no recurrence will be detected. In Chapter 5 additional imaging with a diagnostic radioactive iodine (I-131) whole body scan is discussed (DxWBS). This procedure was routinely performed in all DTC patients during follow-up. At the time of our research, DxWBS was no longer recommended as a routine diagnostic procedure for low-risk patients. Our study therefore focused on high-risk patients. It showed that routine performance of a DxWBS, in addition to Tg measurement and ultrasound of the neck, had limited diagnostic value. PROGNOSIS In a large number of DTC patients (20-50%) the cervical lymph nodes are involved. The role of the number and location of lymph node metastasis is discussed in Chapter 6. We investigated whether the number of lymph node metastasis and/or the location (central vs lateral compartment) had prognostic significance. Studies from Japan show that the number of lymph nodes in the lateral compartment (>5) had prognostic significance. The difficulty of applying these results to European and American guidelines lies in the different treatment of DTC patient in Japan. The only factor that significantly influenced recurrence rate and disease-free survival in our study was the presence of lymph node metastasis in the lateral compartment.