BACKGROUND: Neuroendocrine neoplasms (NENs) are rare tumours with variable clinical behaviour. Their natural history is ideally best approached in large, multicentre and multinational registries with long-term patients' follow-up. The European Neuroendocrine Tumour Society registry aims to obtain information regarding NEN outcomes and prognostic factors in a European frame. PATIENTS AND METHODS: We collected data from 7 national NEN registries (Belgium, Czech Republic, Germany, Greece, Poland, Spain, Switzerland), representing 10,102 patients. Anonymised/pseudonymised data were collected in a secured server. Descriptive statistical methods were applied, as well as Kaplan-Meier survival curves and multivariable analyses for prognostic factors of overall survival (OS). RESULTS: median age of the study population was 60 years (range: 18-102), 48% were female. Common primary tumour sites were pancreas (27%) and small intestine (21%). Stage 4 disease was found in 47% of patients, while 26/10/16% had stage 1/2/3 disease, respectively. Grading (n = 6952) was G1/2/3 in 48/37/15% of the patients, respectively. Surgery was the main treatment, provided to 71% of patients, followed by somatostatin analogues (32%), chemotherapy (20%), Peptide receptor Radionuclide Therapy (PRRT) (9%) and targeted therapies (8%). OS at 5 years was 74%, influenced by grade, stage and tissue of origin in multivariate analysis. A Ki67 cut-off value set at 55% within the G3 group allowed to separate 2 groups with a meaningful different OS. CONCLUSION: We report the first analysis of the European Neuroendocrine Tumour Society registry, comprising 10,102 patients with NEN from 7 European countries. This large cohort study describes prognostic factors for the survival of NENs throughout Europe, including primary tumour site, grade, stage and treatment.

Asklepios Kliniken Hamburg Department of Internal Medicine and Gastroenterology Hamburg Germany

Charité University Hospital Berlin Gastroenterology Department Berlin Germany

Charles University Oncological Clinic General Faculty Hospital and 1 st Medical Faculty Praha Czech Republic

Department of Oncology Inselspital Bern University Hospital University of Bern Switzerland

Hepato gastroenterology Unit Cliniques Universitaires Saint Luc Bruxelles Belgium

Hospital Universitario Central de Asturias Medical Oncology Oviedo Asturias Spain

Hospital Universitario de Fuenlabrada Pathology Unit Madrid Spain

Katholieke Universiteit Leuven UZ Leuven Digestive Oncology Hepatology Leuven Belgium

Medical University of Silesia Department of Pathophysiology and Endocrinology Katowice Slaskie Poland

National and Kapodistrian University of Athens Department of General Medicine and Endocrinology Athens Attica Greece

Oncology Department Hospital Universitario 12 de Octubre IIS Imas12 UCM CNIO CIBERONC Madrid Spain

Universitätsspital Basel Endocrinology Diabetology and Metabolism Basel Switzerland

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