Tumour markers: CEA, CA 125, CA 19-9, CA 15-3, TPA
The presence of a tumour in the body can be revealed by measuring particular substances in the blood. However, none of these tests can be used as a tool for prevention or screening, only to support or confirm a diagnosis.
The tumour markers are:
- CEA (carcinoembryonic antigen)
- The mucinous markers, in particular CA 125, CA 19-9 and CA 15-3
- TPA (tissue polypeptide antigen).
Why they are done
These tests are prescribed by the doctor (usually an oncologist) and can be useful to diagnose whether a person has a tumour (bearing in mind that they do not indicate the presence of a tumour exclusively) or to monitor the disease; in fact, they are mainly used for this purpose and help assess whether treatment is effective. If they are abnormal, the treatment should be changed to fight the disease. In particular:
CEA (carcinoembryonic antigen) is a protein that was once thought to be associated only with bowel cancer; it is now known to be associated with other types of cancer too, such as cancer of the breast, lung, ovary, uterus and pancreas. However, it can also be raised by other non-cancerous diseases, such as chronic bronchitis, tuberculosis, liver cirrhosis, ulcerative colitis and pancreatitis, and in some healthy people who smoke heavily.
CA 125 is a marker of ovarian cancer. It is not an early marker and is used mainly to check the progress of treatment.
CA 19-9 is linked to bowel cancer (and to other non-cancerous diseases such as pancreatitis, cystic fibrosis and ulcerative colitis), but it is mainly associated with pancreatic cancer. This is not an early test either.
CA 15-3 rises in breast cancer.
TPA (tissue polypeptide antigen) is a completely non-specific marker, i.e. it rises in many cancerous or inflammatory diseases and reflects the rate of cell turnover (cell production), so it helps the doctor assess when there is a risk that the tumour is progressing quickly.
How they are done
These laboratory tests involve a simple blood sample and require fasting to prevent food from interfering with the result. Taking medicines does not affect the result, except for those specifically used to treat cancer.
Results
NORMAL VALUES
CEA 0-5 ng/ml
CA 125 0-35 U/ml
CA 19-9 0-37 U/ml
CA 15-3 0-29 U/ml
TPA 0-0.09 ng/ml
What CEA means:
• If the result is higher than normal, the doctor will recommend appropriate further tests to assess whether it is a cancer (if it is, the higher the CEA, the more advanced the tumour). If, on the other hand, the tests are done to monitor cancer treatment, an abnormal result indicates that the treatment is not working and must be changed.
CA 125:
• If the result is higher than normal, the doctor will recommend appropriate further tests to assess whether it is a tumour. If, on the other hand, the tests are done to monitor cancer treatment, it means the person is not responding to treatment, which must therefore be changed.
CA 19-9:
• If the result is higher than normal, the doctor will proceed in the same way as for an abnormal CA 125 or CA 15-3.
CA 15-3:
• If the result is higher than normal, the doctor will proceed in the same way as for an abnormal CA 125 or CA 19-9.
TPA:
• If the result is higher than normal but fairly close to the reference value, cell turnover is low; if, however, TPA is high, turnover and production are fast, and this is an unfavourable sign because it means that diseased cells are developing rapidly and spreading through the body. For this reason CEA, which reflects the presence of a tumour mass, is always tested at the same time. If CEA is very high and TPA low, the tumour mass is large but not growing quickly, whereas a low CEA and a high TPA mean that the tumour mass is small but cell production is fast, which is more worrying.