Table 1. Comparison between main types of ctDNA analyses (10).

Testing platform	Advantages	Disadvantages
PCR based platforms (for example: ARMS; BEAMing, ddPCR)	(I) Quick turnaround time; (II) high sensitivity and specificity; (III) relatively cheaper	(I) Can only detect a small number of known relevant mutations; (II) harder to detect copy number variations and gene fusions
NGS based platforms (for example: Tam-Seq, Ampli-Seq, CAPP-Seq, WES, WGS)	(I) Can detect a large number of mutations without limiting sequencing space; (II) easier to detect copy number variations and gene fusions	(I) Longer turnaround time; (II) expensive; (III) bioinformatics required to analyze results

PCR, polymerase chain reaction; NGS, next-generation sequencing; ARMS, amplification refractory mutation system; BEAMing, beads, emulsion, amplification, magnetics; CAPP-Seq, cancer personalized profiling by deep sequencing; ddPCR, droplet digital PCR; Tam-Seq, tagged-amplicon deep sequencing; WES, whole-exome sequencing; WGS, whole-genome sequencing; ctDNA, circulating tumor DNA.