INTRODUCTION Gastroenteropancreatic neuroendocrine neoplasms (GEP‑NENs) constitute a rare and heterogeneous group of tumors with varied biology.

OBJECTIVES The aim of this study was to establish the clinical characteristics of patients with GEP‑NEN and identify factors influencing their 5‑year survival.

PATIENTS AND METHODS The study included 122 patients living in Kraków or its administrative region, who were diagnosed with GEP‑NEN between 2002 and 2011.

RESULTS The mean follow‑up period was 4.9 ±2.8 years. The most frequent primary site of the tumor was the small intestine (n = 25; 20%), followed by pancreas (n = 23; 19%), rectum (n = 23; 19%), stomach (n = 21; 17%), appendix (n = 19; 16%), and colon (n = 11; 9%). There were 84 tumors classified as NEN G1; 31, as NEN G2; 5, as neuroendocrine carcinoma; and 1, as mixed adenoneuroendocrine carcinoma. Most well‑differentiated GEP‑NENs (n = 57; 57%) were diagnosed at stage I according to the American Joint Committee on Cancer / Union for International Cancer Control (AJCC/UICC) classification; 77% of NEN G1 (n = 64) were diagnosed at stage I, but the majority of NEN G2—at stage IV (n = 18; 58%). Metastases at diagnosis were found in 38 patients (34%). In 90% of the cases (n = 101), tumors were hormonally nonfunctional. The overall 5‑year survival was 85%. In the univariate analysis, NEN G2 (P = 0.003), higher stage according to the AJCC/UICC classification (P <0.001), and metastases at diagnosis (P <0.001) were associated with poorer prognosis. In standardized multivariate models, higher stage (P = 0.02) and metastases at diagnosis (P = 0.02) were independent risk factors for death.

CONCLUSIONS The most important factors affecting survival of patients with GEP‑NENs are tumor stage and the presence of metastases at diagnosis. The analysis of single‑center data improves identification of patients with poorer prognosis requiring a more aggressive approach.