EGFR and neoplasm: While ctDNA can be personalized to monitor response to a certain treatment type if the correct biomarker is used (e.g. monitoring the appearance of RAS mutations in response to anti-EGFR treatment, where measuring genetic markers is essential), it can also be used for ultrasensitive monitoring of tumor burden where biomarker selection is less important and is very easily achieved with simpler technology (e.g., utilizing epigenetic biomarkers).