Utility of circulating tumor DNA in cancer diagnostics with emphasis on early detection

Table 3 Ratio of fetal/maternal DNA in maternal circulation

Weight of fetus/placental unit^a	Percentage fetal DNA in maternal plasma	Ratio of fetal to maternal DNA in maternal circulation	Whole fetal/cancer genome equivalents per 4 mL of plasma^b	Number of malignant cells in tumor of this size^c	Likelihood of successful cancer detection
0.5 kg	10	1:10	1000	10 ¹²	High
100 g	2	1:50	200	10¹¹	High
10 g	0.2	1:500	20	10¹⁰	Moderate
1g^d	0.02	1:5000	2	10⁹	Low
100 mg^d	0.002	1:50,000	< 1	10⁸	Very low
10 mg	0.0002	1:500,000	< 1	10⁷	Unlikely
1 mg	0.00002	1:5,000,000	< 1	10⁶	Unlikely

^aBold numbers indicate experimental data
^b1 mL of blood contains approximately 2400 whole genome equivalents in pregnant women and normal individuals [40, 41]
^cCalculated by extrapolation of data mentioned by Uvili et al. [34]
^dThese ranges have been reported as thresholds for successful detection of cancer based on ctDNA by the most sensitive techniques available to date [29, 60, 61]

ISSN: 1741-7015