Meta‐analysis of the diagnostic value of exosomal miR‐21 as a biomarker for the prediction of cancer

Background Early diagnosis of cancer is still the most effective method to increase survival and therapeutically effective patient management. Accumulating studies had exploited exosomes as an indicator for the diagnosis and prognosis of cancer. In addition to exosomes, exosome‐derived miRs are widely investigated as a novel biomarker for diagnosis in cancer patients. The aim of this study was to clarify the diagnostic value of ex‐miR‐21 in cancer. Methods Databases were searched for eligible studies up to June, 2021. Studies included in this meta‐analysis were reviewed and selected independently by two authors. The data of sensitivity, specificity, diagnostic odds ratio (DOR), and summary receiver operating characteristic curves (SROC) of exosomal miR‐21 as a diagnostic biomarker were extracted and calculated. Quality assessment was conducted by using the QUADAS‐2 tool. Results A total of 26 studies were included in the systematic analysis and meta‐analysis. The pooled results of sensitivity, specificity, PLR/NLR, DOR, and area under the curve were 76% (95%CI, 0.70–0.81), 82% (0.77–0.87), 4.3 (3.1–6.0), 0.29 (0.22–0.38), 15 (8–26), and 0.86 (0.83–0.89), respectively. Sensitivity analysis and Deeks' funnel plot indicated that results remained unchanged and had no publication bias. For the subgroup analysis, it was showed that ex‐miR‐21 had a superior diagnostic accuracy on identifying PC. Conclusion Exosomal microRNA‐21 can serve as an effective and widely used diagnostic biomarker for cancer, especially in PC. The using field of exosomes and exosome‐derived miR can further extend the prognosis and therapeutic management. Standardized isolation of exosomes and miRNA‐21 should be developed. The role of miR‐21 as a potential serum/plasma biomarker has been determined while they are still unperforming in cancer diangosis. Currently, the application of miR‐21 from exosomes has been demonstrated and its diagnostic accuracy should be identified as well.