Long-term survival and prognostic factors in neuroendocrine tumors: Results from a large multicenter study.

1604 Background: The clinical behavior of neuroendocrine tumors (NET) is highly variable, but the only data available in literature on large series are mainly based on retrospective register data collected in 3-5 decades, focusing on short-term follow-up. These are clearly insufficient due to the frequent evolution in classification criteria, diagnostic techniques and the scarcity of clinical data. Methods: Data from a total of 1659 NET patient were collected from 12 Italian referral centers. A specific software was developed for the study. Only patients with histological diagnosis revised according to the WHO Classification in active long term follow-up in the period 1990-2010 were included in the study. Patients with incomplete diagnostic work-up, without clinical data or lost at follow-up were excluded. Cumulative survival were analyzed according to site of origin, histotype, grading, ki67 score, secreting pattern (functioning or not functioning) and staging. Results: At 2 yr cumulative survival do not...