Survival trends of metastatic small intestinal neuroendocrine tumor: a population-based analysis of SEER database

Background: Incidence of small intestinal neuroendocrine tumors (SNETs) is increasing and they now comprise the most common types of small intestinal cancer. SNETs frequently present with distant metastasis. Significant uncertainty prevails with regards to the surgical management strategies in metastatic SNETs. Therefore, we aim to analyze survival trends in metastatic SNET patients stratified by type of surgical treatment.

Methods: We analyzed the data from the SEER database: Incidence - SEER 18 Regs Research Data + Hurricane Katrina Impacted Louisiana Cases, Nov 2016 Sub (1973-2014 varying). Relative survival rates (RSRs) and hazard ratios (HRs) were measured for patients diagnosed with metastatic SNET between 2000 and 2014. Treatment received was divided into two broad categories; surgical resection and no surgery and further subcategorized into local resection (LR) (surgery of the primary tumor only) and radical resection (RR) (surgery for primary tumor and metastasectomy).

Results: We identified 1,138 metastatic SNET cases. Median age was 61 years. Median survival was 41 months and 5 year RSR was 72%. Age >50 years (HR 2.10, P<0.001), poorly differentiated histology (HR 3.50, P<0.001) and tumor size >2 cm (HR 1.27, P=0.07), showed poor outcome. The group which did not receive any tumor directed surgery showed the worst survival (5 years RSR 45.30% vs. 76%, respectively for no surgery vs. surgery group, P<0.001). We found no significant difference in survival between LR and RR (HR 1.01, 95% CI: 0.73-1.40, P=0.92). Upon further stratification, surgery significantly improved survival on patients who were >50 years (HR 0.37), and for primary tumor location in the duodenum (HR 0.13).

Conclusions: Surgery for the primary tumor (LR or RR) significantly improved 5-year survival even in the presence of distant metastasis irrespective of primary tumor size, grade, or histology. Poor prognostic factors include, age >50 years, duodenal primary, tumor size >2 cm, and poorly differentiated histology.