5. Conclusions and Prospect
Based on the accuracy of this initial meta-analysis and very close cutoff values from different
experimental conditions, methods and internal controls, exosomal miR-21 has a very strong potential
to be a good general biomarker for cancer diagnosis. The results of exosomal miR-21 seemed to be
better than those of circulating miR-21 according to several comparisons we discussed above, but
we know the case number was too small to give a very strong conclusion. Although the sample size
was small in this study, determining and understanding the characteristics of different candidates as
biomarkers for cancers are important topics in the development of the best diagnostic methods for
early stages of cancers in order to increase the survival rates of the patients.
Prospectively, combining the right miRNA panels or cancer antigens may give better diagnostic
results or prognostic predictions in most circumstances. To make a better diagnosis, we should also
pay more attention to choosing correct, stable and consistent internal controls or internal control panels.
For a general biomarker, other issues, including qPCR reagents and exosome-isolating methods, also
need to be standardized. In addition, an in-depth study of various diseases for miR-21 would allow
better application for cancer diagnosis.