For instance, typical circulating tumor markers are great importance for monitoring therapy in metastatic colorectal (carcinoembryonic antigen, CEA), prostate (prostate specific antigen, PSA), ovarian (carbohydrate antigen, CA125), breast (CA15-3 and CA 27.29), and pancreatic (CA 19-9) cancer patients26–29. Here, CEACAM5 is linked to cancer.