Limitation
METASTASES
The current study included various limitations due to the nature of the database, which should be considered when interpreting the results. To begin, because this was a retrospective study, selection bias was unavoidable. Second, the SEER database lacked information on precise data on performance status, comorbidities, varied chemotherapy regimens, treatment for distant metastases, somatostatin analogues, and “neuroendocrine cancer-specific” data. Furthermore, the SEER database’s GNEC classification was not completely the same as the WHO classification. Finally, even though the research was externally validated, the small sample data could only provide limited support for the result. Multicenter data with a larger sample size are required to further evaluate the predictive model.