Diagnosis and staging
Tumour markers
CEA, CA 19-9, CA 125Substances measurable in blood that give an indication of a tumour's activity and of its response to treatment. They cannot diagnose on their own and must be interpreted alongside imaging and clinical findings.
The three most used in digestive and peritoneal tumours are CEA, associated with colorectal cancer; CA 19-9, with pancreatic, biliary and appendiceal tumours; and CA 125, with ovarian cancer and with peritoneal involvement in general.
They can rise without cancer (smoking, cholestasis, pancreatitis, endometriosis, peritoneal irritation) and they can be normal with advanced disease. That is why they neither diagnose nor rule out on their own.
Their value lies in the trend over time, always measured in the same laboratory: a fall supports response to treatment and a sustained rise may anticipate imaging.
This explanation is intended as general information and does not replace a specialist assessment of an individual case.
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