Epidemiology and classification of gastroenteropancreatic neuroendocrine neoplasms using current coding criteria

Background: The lack of uniform criteria for coding of gastroenteropancreatic neuroendocrine neoplasia (GEP-NEN) has hampered previous epidemiological studies. The epidemiology of GEP-NEN was investigated in this study using currently available criteria. Methods: All patients diagnosed with GEP-NEN between January 2003 and December 2013 in a well defined Norwegian population of approximately 350 000 people were included. Age-and sex-adjusted incidence rates were calculated. The current 2010 World Health Organization criteria, European Neuroendocrine Tumour Society classification and International Union Against Cancer (UICC) classification were used. Results: A total of 204 patients (114 male, 55.9 per cent) were identified. The median age at diagnosis was 61 (range 10-94) years. The annual overall crude incidence was 5.83 per 100 000 inhabitants, with an increasing trend (P = 0.033). The most frequent location was small intestine (60 patients, 29.4 per cent) followed by appendix (48 patients, 23.5 per cent) and pancreas (33 patients, 16.2 per cent). Grade 1 tumours were more common in gastrointestinal (100 patients, 58.5 per cent) than in pancreatic (9 patients, 27 per cent) NEN. According to the UICC classification, 77 patients (37.7 per cent) had stage I, 17 patients (8.3 per cent) stage II, 37 patients (18.1 per cent) stage III and 70 patients (34.3 per cent) had stage IV disease. No patient with stage I disease had grade 3 tumours; advanced tumour grade increased with stage. Conclusion: A high crude incidence of GEP-NEN, at 5.83 per 100 000 inhabitants, was noted together with a significant increasing trend over time.