The correlation coefficients between the ctDNA/CEA level and tumor diameter were similar in all patients and the group that included patients with liver metastasis (all patients: ctDNA: r = 0.45, p < 0.0001; CEA: r = 0.69, p < 0.0001; liver metastasis: ctDNA: r = 0.49, p < 0.0001, CEA: r = 0.40, p < 0.0001) (Figures 2 and 3). Here, CEACAM5 is linked to neoplasm.