Table 1. PICOT eligibility criteria.

P	Population	Male patients of any age worldwide diagnosed with PCa.
I	Index prognostic factor	Measurement of miR-21 levels in tissue or circulating/fluid samples such as tumour tissue, blood, plasma, serum, urine and seminal fluid.
C	Comparator prognostic factors	Clinicopathological factors such as stage, grade, Gleason score, PSA level and health condition (e.g., recurrence, metastasis).
O	Outcomes of interest	Survival outcomes of any type (e.g., OS, RFS) estimated in HR, 95% CI, P-value and/or survival curves with log-rank P-value.
T	Timing	Samples taken as baseline at the start of follow-up of any length.

Studies with characteristics specified by PICOT were eligible for inclusion in meta-analysis.

Abbreviations: CI, confidence interval; HR, hazard ratio; OS, overall survival; PCa, prostate cancer; PSA, prostate-specific antigen; RFS, recurrence-free survival.