Prognostic significance of circulating microRNA-21 expression in esophageal, pancreatic and colorectal cancers; a systematic review and meta-analysis

Background: Literature has shown that aberrantly expressed microRNAs may have implications in certain cancers. A wealth of studies signal potential prognostic role of microRNA-21 in GIT cancers. This meta-analysis quantitatively determines prognostic significance of circulating microRNA-21 in esophageal squamous cell carcinoma (ESCC), pancreatic ductal adenocarcinoma (PDAC) and colorectal carcinoma (CRC). Methods: Databases of Medline, Wiley online library, Cochrane library, Taylor and Francis Online, CINAHL, Springer, Proquest, ISI Web of knowledge, ScienceDirect, and Emerald were searched using MeSH terms serum/tissue microRNA-21, prognosis, esophagus squamous cell carcinoma, pancreatic ductal adenocarcinoma, colorectal cancer. A systematic algorithm was used that selected 15 relevant studies. Meta-analysis was conducted using forest plot and a summary effect model was employed. Results: This meta-analysis reports significant prognostic value of miR-21 in predicting worse overall survival (OS) in ESCC, PDAC, and CRC with pooled hazard ratio (HR) of 3.49 (95% CI 2.58-4.71, p-value < 0.01). Subgroup analysis for ESCC showed a pooled HR of 3.46 (95% CI 1.88-635, p value of < 0.01), worse overall survival (OS) with the pooled HR of 3.14 (95% CI 2.22-4.43, p value < 0.01) for CRC and a pooled HR of 3.77 (95% CI 1.63-8.73, p value < 0.01) for PDAC. Conclusion: This research infers that microRNA-21 expression is a powerful prognostic tool. Expression of microRNA-21 is associated with poor OS and poorer disease-free survival in ESCC, PDAC and CRC.