Table 2.
Univariate association between tumor response at first imaging, CEA and ctDNA indices (N = 42)
| Variable | Tumor responsea |
P value | |
|---|---|---|---|
| No response | Response | ||
| Patients (N, %) | 20 (47.6) | 22 (52.4) | |
| CEA, pretreatmentb, median (IQR) | 46 (18–660) | 16.9 (10–89.5) | 0.171 |
| CEA after one cycle of chemotherapy, median (IQR) | 50.4 (19–520) | 11.3 (6.6–84.9) | 0.173 |
| Fold change in CEA, median (IQR) | 0.92 (0.78–1.11) | 0.91 (0.67–1.33) | 0.884 |
| ctDNA, pretreatment, median (IQR) | 12.9 (0.6–29.7) | 20.8 (2.7–34.5) | 0.339 |
| ctDNA after one cycle of chemotherapy, median (IQR) | 3.7 (0.3–6.6) | 0.4 (0.2–5.3) | 0.182 |
| Fold change in ctDNA (no. of patients, %) | 0.016 | ||
| <10-fold reduction | 15 (75.0) | 8 (36.4) | |
| ≥10-fold reduction | 5 (25.0) | 14 (63.6) | |
P value indicates a significance level of <0.05.
aDefined as ≥20% reduction in the sum of largest diameters according to standard RECIST criteria.
bCEA not collected before treatment in two patients.