Small intestinal neuroendocrine tumors (SI-NETs) are uncommon, with an annual incidence of about 1 per 100,000 individuals. The primary tumor (PT) is generally small, but nevertheless the majority of patients have mesenteric lymph node metastases and liver metastases at diagnosis. Our aim was to identify prognostic factors for survival and to evaluate outcome after surgery in SI-NET patients.

We included 603 consecutive patients (325 men; age at diagnosis 63 ± 11 years [mean ± SD]) with histopathologically verified SI-NET, who were diagnosed between 1985 and 2010. Hospital charts were reviewed and were scrutinized for carcinoid heart disease (CHD), flush and/or diarrhea, proliferation by Ki-67 index, mesenteric lymph node metastases (m.lgllm), distant abdominal lymph node metastases (da.lgllm), liver tumor load (LTL), extra-abdominal metastases (EAM), locoregional resective surgery, as well as debulking of LTL, and adverse events after surgery.

Median overall survival (OS) was 8.4 years; 5-year OS was 67%, and 5-year relative survival was 74%. Independent prognostic factors by univariate and multivariate analysis were age at diagnosis, CHD, m.lgllm, da.lgllm, LTL, EAM, peritoneal carcinomatosis (PC), and proliferation. Locoregional resective surgery was associated with increased survival on crude and multivariate analysis. The 30-day mortality in our institution after initial locoregional resective surgery was 0.5% (1/205).

For the first time, m.lgllm and da.lgllm, LTL, PC, and EAM are demonstrated to be independent prognostic factors by multivariate analysis. Locoregional removal of the PT/m.lgllm. was a positive prognostic factor by crude and adjusted analysis and may influence survival.