A prognostic nomogram in patients with distant metastasis of pancreatic neuroendocrine tumors: a population-based study. 
Aim: Prognostic factors in patients with distant metastatic pancreatic neuroendocrine tumors (PNETs) remain uncertain.  The purpose of our study is to establish a nomogram to predict survival outcomes in patients with metastatic PNETs.  Methods: A total of 878 patients diagnosed with PNETs in the Surveillance, Epidemiology and End Results database between 2004 and 2016 were retrospectively identified.  The Kaplan-Meier survival analysis with log-rank test was used to analyze survival outcomes.  The nomogram was established after a univariate and multivariate Cox analysis.  Results: The independent prognostic variables, including age, tumor grade and primary site surgery were applied to develop a nomogram.  The original concordance index was 0.773 (95% CI: 0.751-0.795), and the bias-corrected concordance index was 0.769 (95% CI: 0.748-0.791).  The internal calibration curves showed well consistency and veracity in predicting cancer-specific survival probabilities.  Conclusion: A nomogram was constructed and verified to predict survival outcomes in patients with distant-stage PNETs.