3. Epidemiology of Neuroendocrine Tumors

Neuroendocrine tumors (NETs) arise from neuroendocrine cells in the endocrine and central nervous systems. NETs are responsible from approximately 0.5 % of all cancers. The incidence has gradually increased during the last three decades. The crude incidence is about 0.2/100,000. It increases with age and peaks between 50 and 70 years. Due to slowly growing nature of NETs, its prevalence is increasing. The prevalence has been estimated to be 35/100,000/year. Most of NETs are diagnosed at advanced stages. Gastrointestinal tract is the most common location and is responsible for two-thirds of NETs. Most of them were diagnosed at the localized stage. However, NETs originating in pancreas tend to be aggressive and about 60 % of these tumors are malignant at the time of diagnosis. The prognosis of NETs associates with their location, functional status, differentiation, and initial stages. The best survival rates are observed in patients with NETs arising in the rectum and appendix.