Table 2. Subgroup analysis for overall survival.
| Subgroups | No. of Studies | HR | 95% CI | I2 |
| Tumor Stage | ||||
| I-IV | 7 | 3.37 | 2.22-5.12 | 55.2% |
| I-II | 12 | 2.95 | 2.11-4.12 | 28.0% |
| III-IV | 15 | 2.01 | 1.58-2.57 | 89.0% |
| Sampling Time | ||||
| Baseline | 30 | 2.42 | 1.95-3.01 | 88.4% |
| Post-operative | 4 | 4.84 | 2.38-9.85 | 0.0% |
| Detection Marker | ||||
| K-ras | 20 | 3.31 | 2.53-4.34 | 48.6% |
| K-ras G12V | 7 | 2.03 | 1.51-2.74 | 49.3% |
| K-ras G12D | 4 | 1.77 | 1.22-2.58 | 55.6% |
| ERBB2 exon17 | 1 | 1.73 | 1.10-2.72 | 0.0% |
| ctDNA level | 4 | 1.40 | 1.07-1.83 | 87.2% |
| Detection Method | ||||
| PCR | 9 | 3.77 | 1.77-8.02 | 81.6% |
| ddPCR | 17 | 2.36 | 1.90-2.94 | 62.3% |
| NGS | 5 | 2.14 | 1.17-3.91 | 85.4% |
| Safe-Sequencing System | 2 | 4.35 | 1.67-11.32 | 0.0% |
| PCR&NGS | 1 | 1.42 | 1.19-1.69 | 0.0% |
| ctDNA(+) Rate | ||||
| <40% | 19 | 3.08 | 2.22-4.28 | 74.1% |
| >40% | 15 | 2.01 | 1.58-2.55 | 84.6% |
| Sample Origin | ||||
| Plasma | 30 | 2.60 | 2.08-3.26 | 88.6% |
| Serum | 4 | 2.05 | 1.16-3.65 | 36.1% |
| Ethnicity | ||||
| Asian | 18 | 2.49 | 1.90-3.28 | 73.2% |
| Caucasian | 16 | 2.47 | 1.85-3.30 | 85.5% |
| Patient Size | ||||
| <50 | 15 | 3.14 | 2.01-4.90 | 60.3% |
| 50-100 | 8 | 3.10 | 1.58-6.09 | 93.6% |
| >100 | 11 | 1.91 | 1.60-2.27 | 55.1% |