Background: Extra-pulmonary neuroendocrine carcinomas (EP-NEC) are rare tumours that require expertise for correct and timely diagnosis, which is essential for clinical decision making. The number of patients affected, treatment given, and the proportion surviving the disease is based on limited evidence. The aim of this study is to retrospectively analyse the incidence, treatment, and relative survival (RS) of EP-NEC patients in the Netherlands. Methods: Patients diagnosed between 2008-2012 with EP-NEC or NEC with unknown primary site (UP-NEC) were selected from the Netherlands Cancer Registry based on combinations of tumour localisation and morphology code. Incidence was studied using the European standardised (ESR) and world standardised rates, and RS was calculated using the Ederer II method. Results: In total, 1,544 cases were analysed, 1,045 EP-NEC and 499 UP-NEC. For EP-NEC, the incidence was 1.0 per 100,000 person-years (ESR), the mean age was 68 years, and the male to female ratio was 1: 0.6. Most frequent EP-NEC localisations were the bladder and the gastrointestinal tract, and the treatment most frequently given was surgery in combination with chemotherapy. The overall 5-year RS was 38% for patients with local/regional disease (n = 447), and 7% for patients with extensive disease (n = 582). For UP-NEC patients (n = 499), the 5-year RS was 6%. Conclusions: This study is the first nationwide study presenting an increase in the incidence of EP-NEC patients from 196 to 260 cases annually in the Netherlands. The best 5-year RS was found for EP-NEC patients with local disease located in the bladder, where the worst 5-year RS was found for patients with disease located in the oesophagus.

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Keywords Cancer registry, Extra-pulmonary neuroendocrine carcinoma, Incidence, Population based study
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Journal Neuroendocrinology: international journal for basic and clinical studies on neuroendocrine relationships
Van Der Zwan, J.M. (Jan Maarten), Siesling, S, Van Velthuysen, L. (Loes), Links, T.P, Walenkamp, A.M.E, & Tesselaar, M. (Margot). (2018). Extra-Pulmonary Neuroendocrine Carcinomas: A Population-Based Study in the Netherlands. Neuroendocrinology: international journal for basic and clinical studies on neuroendocrine relationships, 107(1), 50–59. doi:10.1159/000488987