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This meta-analysis aims to evaluate the long-term survival and prognostic factors in patients with metastatic small intestine neuroendocrine tumors (siNETs). Patients with siNETs usually present with advanced disease, limiting curative treatment options. The overall survival seems favorable compared to other cancers, but differences in terminology, lack of consistent coding, conflicting results from smaller cohorts, and recent developments of new treatment options make (reliable) survival data difficult to achieve. Nevertheless, accurate survival data are essential for many facets of health care. A systematic literature search was performed using MEDLINE®(PubMed), EMBASE®, Web of Science, and Cochrane Library up to June 30, 2021. Studies were included if the overall survival data in patients with metastatic siNETs were reported. The results were pooled in a random-effects meta-analysis and are reported as hazard ratios and 95% CIs. Subgroup analyses and meta-regression were performed to assess the observed heterogeneity and the impact of important prognostic factors. After screening 9065 abstracts, there were 23 studies, published between 1995 and 2021, that met the inclusion criteria, with a total of 8636 patients. The weighted 5- and 10-year overall survival was 67 and 37%, respectively. Meta-regression identified younger age and primary tumor resection to be associated with better prognosis. Subgroup analyses showed similar results. This study confirms that in an advanced, metastatic setting, the weighted 5- and 10-year overall survival reveal a favorable prognosis, improving over the last few decades. Meta-regression showed that age at diagnosis is an important prognostic factor.