CEACAM5 and cancer: Traditional serologic testing used for diagnosis and management of breast cancer relies on carcinoembryonic antigen (CEA) for cancer detection and monitoring recurrence, carbohydrate antigen 15.3 (CA15.3) for monitoring metastatic (stage 4) breast cancer and its response to treatment and carbohydrate antigen 27.29 (CA27.29) for predicting recurrence.