They also found that the circulating exosomal ddDNA was a promising tumor-based mutation biomarker that could be used to validate cancer diagnostics and prognostics by identifying multiple genes, such as EGFR, BRAF, RAS, IDH, and HER2, because (1) it is stable, (2) it is biocompatible, and (3) its functional group can be modified [127,128]. Here, EGFR is linked to cancer.