Diagnostic and predictive value of liquid biopsy-derived exosome miR-21 for breast cancer: a systematic review and meta-analysis

Background and purpose Studies have revealed that miR-21 is abnormally expressed in breast cancer patients, suggesting that miR-21 could be exploited as a possible diagnostic biomarker for clinical applications. In order to provide clinical evidence that is supported by research, we investigate the diagnostic utility of miR-21 in breast cancer in this study.Methods From their inception to 23 January 2022, the PubMed, EMBASE, Web of Science, Cochrane Library, and Scopus databases were searched for all pertinent English literature. QUADAS-2 for literature quality assessment, GRADE for evidence grading. Statistical analyses were performed using the R 4.0.1 and Revman 5.3. The results were validated using Stata 15.1 software. Subgroup analysis was also performed according to the source of miR-21 and miR-21 combinations.Results Nine publications with 2048 patients were reviewed for inclusion. All of the included studies are of moderate-high quality. Meta-analysis was performed using a mixed-effects model. The pooled sensitivity, specificity, diagnostic odds ratio (DOR), negative likelihood ratio (NLR) and positive likelihood ratio (PLR) were 0.91 [95% CI (0.86, 0.95)], 0.85 [95% CI (0.77, 0.91)], 56.62 [95% CI (21.00, 184.83)], 0.11 [95% CI (0.05, 0.18)] and 6.35 [95% CI (3.66, 11.16)], respectively. The GRADE classification for miR-21 was A, indicating a strong recommendation for breast cancer screening.Conclusions The available evidence suggests that miR-21 has sufficient diagnostic value as a biomarker for breast cancer. Its diagnostic precision can be further improved by combining it with other miRNAs. Based on the GRADE review, miR-21 is strongly recommended for breast cancer screening.