Objective: The aim of this study was to investigate the prognostic value of mircoRNA-17 and mircoRNA-17-5P (miR-17/17-5P) in patients with cancer. 
Materials and methods: We conducted a comprehensive search on published literature following the guidelines of the meta-analysis of observational studies in epidemiology group for design, implementation, and reporting. The methodological qualities for included studies were assessed using the quality in prognosis studies. The pooled hazard ratios (HRs) with 95% CIs for overall survival (OS) and progression-free survival/recurrence-free survival/disease-free survival (PFS/RFS/DFS) were calculated to appraise the associations between miR-17/17-5P expression and cancer prognosis. 
Results: A total of 21 studies involving 2099 subjects were analyzed in evidence synthesis. The results showed that high expression of miR-17 was associated with poor OS (HR=2.14; 95% CI: 1.69–2.71, P <0.001) in patients with cancer, especially in Caucasian (HR=2.23; 95% CI: 1.58–3.14, P <0.001) and digestive tract cancer (HR=1.29, 95% CI: 1.03–1.63, P =0.03), and miR-17 expression was significantly correlated with PFS/RFS in cancer patients (HR=1.69, 95% CI: 1.29–2.22, P <0.001). miR-17-5P overexpression was significantly linked with poor OS in cancer patients (HR=1.66; 95% CI: 1.31–2.09, P =0.00), especially in Asian (HR=1.81; 95% CI: 1.37–2.40, P <0.001), digestive tract cancer (HR=1.80; 95% CI: 1.29–2.50, P <0.001), and serum sample (HR=1.76; 95% CI: 1.29–2.41, P <0.001). miR-17-5P expression was significantly associated with DFS in cancer patients (HR=1.58, 95% CI: 1.07–2.35, P =0.02). 
Conclusion: High expression of miR-17 and miR-17-5P are significantly associated with poor survival in patients with cancer. This indicated that miR-17/17-5P may be a novel prognostic indicator in cancer.
Keywords: miR-17/17-5P, prognosis, cancer, meta-analysis