CEACAM5 and neoplasm: ELISA assessment of blood CEA levels demonstrated a lower blood CEA level (12.6 ± 1.8 ng/mL) in animals with smaller tumor burden (0.1 ± 0.02 g) compared to animals with larger tumor burden [(0.64 ± 0.1 g, 1074 ± 700 ng/mL), Figure 2].