TP53 and cancer: The current system is designed for KRAS and the hotspot region of TP53, which cover up to 50% of the cancer population, but the system can easily be extended to include other genes, such as PI3KCA, PTEN and EGFR. Our standard assay protocol uses plasma cfDNA from 1 ml of whole blood for a single reaction,16 and this system can process 2–4 DNA fragments that are ∼100 bp long in a single reaction.