Table 3.
Weight of fetus/placental unita | Percentage fetal DNA in maternal plasma |
Ratio of fetal to maternal DNA in maternal circulation |
Whole fetal/cancer genome equivalents per 4 mL of plasmab | Number of malignant cells in tumor of this sizec | 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 |
1gd | 0.02 | 1:5000 | 2 | 109 | Low |
100 mgd | 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]