We used preoperative and postoperative plasma samples of patients treated for primary colorectal carcinoma and then it‘s liver metastases and the corresponding FFPE tissue samples together with long-term clinical data for determining of the prognostic significance of mutated KRAS level determined by the ddPCR method even in combination with routinely determined tumor marker CEA. The gene discussed is CEACAM5; the disease is colorectal carcinoma.