Prognostic value of microRNA-21 in pancreatic ductal adenocarcinoma: a meta-analysis

BACKGROUND: Recently, microRNA-21 (miR-21) has been reported to be associated with prognosis of pancreatic ductal adenocarcinoma (PDAC). The present studies aimed to evaluate the prognostic value of miR-21 for PDAC with meta-analysis. METHODS: A systematic search in the PubMed and other databases was conducted to identify eligible studies. The pooled hazard ratios (HRs) with 95 % confidence interval (CI) were calculated. The meta-analysis was conducted using the STATA 12.0 software. RESULTS: A total of 12 articles (13 studies) which included 963 cases were selected for the meta-analysis. Elevated miR-21 expression was significantly predictive of poor overall survival (HR = 2.05, 95 % CI 1.71–2.46, P < 0.001). In the subgroup analyses, similar results were observed in Asian (HR = 2.09, 95 % CI 1.62–2.71, P < 0.001) and Caucasian (HR = 2.36, 95 % CI 1.53–3.65, P < 0.001); in tissue sample (HR = 2.14, 95 % CI 1.73–2.65, P < 0.001) and serum sample (HR = 1.84, 95 % CI 1.30–2.60, P = 0.001); with quantitative real-time polymerase chain reaction assay method (HR = 2.31, 95 % CI 1.86–2.86, P < 0.001); and in patients receiving adjuvant chemotherapy (HR = 2.37, 95 % CI 1.88–3.00, P < 0.001). The association between miR-21 expression level and lymph node metastasis was statistically significant (OR = 1.45, 95 % CI 1.02–2.06, P = 0.038). However, no significant relationship between miR-21 expression level and sex or vascular invasion or neural infiltration was observed (P > 0.05). CONCLUSIONS: Our meta-analysis indicated that elevated miR-21 expression level can predict poor prognosis in patients with PDAC.