was widely reported.This initial systematic review
analyzes the potential role of exosomal miR-21 as a general biomarker for cancers. A total of 10 studies
involving 318 patients and 215 healthy controls have covered 10 types of cancers. The sensitivity and
specificity of pooled studies were 75% (0.70–0.80) and 85% (0.81–0.91), with their 95% confidence
intervals (CIs), while the area under the summary receiver operating characteristic curve (AUC) was
0.93. Additionally, we examined and evaluated almost all other issues about biomarkers, including
cutoff points, internal controls and detection methods, from the literature. This initial meta-analysis
indicates that exosomal miR-21 has a strong potential to be used as a universal biomarker to identify
cancers, although as a general biomarker the case number for each cancer type is small. Based on
the literature, a combination of miRNA panels and other cancer antigens, as well as a selection of
appropriate internal controls, has the potential to serve as a more sensitive and accurate cancer
diagnosis tool. Additional information on miR-21 would further support its use as a biomarker
in cancer.