Guidelines on the use of tumour markers
Tumour markers are substances that can be detected in the blood, urine, or body tissues of patients with some cancers. Tumour markers are produced either by the tumour or by the body in response to the cancer; and also by some benign conditions. Measurements of tumour markers in blood can be useful--when used along with x-rays or other tests--in the detection and diagnosis of some types of cancer. However, measurements of tumour marker levels alone are not sufficient to diagnose cancer for the following reasons:
- Tumour marker levels can be elevated with benign conditions.
- Tumour marker levels are not elevated in every person with cancer.
- Tumour markers are not specific to a particular type of cancer.
The main role of tumour markers is in the monitoring of cancer treatment since there is very little evidence to support their use in screening or diagnosis
Prostate-specific antigen (PSA) is present in low concentrations in the blood of all adult males. It is produced by the healthy and diseased prostate gland. Elevated concentration of PSA may be found in the blood of men with benign prostate conditions, such as prostatitis and benign prostatic hyperplasia, or with prostate cancer. PSA cannot distinguish between benign prostate conditions (which are very common in older men) and cancer, although high values of PSA help to determine who should have further investigations.
CA 125 is produced by a variety of cells, but particularly by ovarian cancer cells. Many women with ovarian cancer have elevated CA 125 levels which is primarily used in the treatment for ovarian cancer. Other cancers associated with elevated CA 125 levels include uterus, cervix, pancreas, liver, colon, breast, lung, and digestive tract.
Non malignant conditions that can cause elevated CA 125 levels include hypothyroidism, endometriosis, pelvic inflammatory disease, peritonitis, pancreatitis and liver disease. Patients with ascites, pleural effusions and heart failure also have elevated values. Menstruation and pregnancy can also cause an increase in CA 125.
CEA is normally found in small amounts in the blood of most healthy people. The primary use of CEA is in monitoring colorectal cancer, especially when the disease has metastasized. However, a wide variety of other cancers can produce elevated levels of this tumour marker, including melanoma, lymphoma, and cancers of the breast, lung, pancreas, stomach, cervix, bladder, kidney, thyroid, liver, and ovary.
Non malignant conditions that can cause elevated CEA levels include inflammatory bowel disease, pancreatitis, and liver disease. Patients who smoke can have raised levels of CEA.
AFP is normally produced by a developing fetus. AFP levels begin to decrease soon after birth and are usually undetectable in the blood of healthy adults (except during pregnancy). An elevated level of AFP strongly suggests the presence of either primary liver cancer or germ cell cancer (cancer that begins in the cells that give rise to eggs or sperm) of the ovary or testicle. Only rarely do patients with other types of cancer have elevated levels of AFP.
Non malignant conditions that can cause elevated AFP levels include benign liver conditions, such as cirrhosis or hepatitis, ataxia telangiectasia, Wiscott-Aldrich syndrome, and pregnancy.
Human Chorionic Gonadotropin (hCG)
hCG is normally produced by the placenta during pregnancy. It is also used to diagnose choriocarcinoma (a rare cancer of the uterus) and to monitor the treatment of trophoblastic disease (a rare cancer that develops from an abnormally fertilized egg). Elevated hCG levels may also be used to monitor treatment of cancers of the testis, ovary, liver, stomach, pancreas, and lung. Marijuana use can also cause elevated hCG levels.
Initially found in colorectal cancer patients, CA 19-9 has also been identified in patients with pancreatic, stomach, and bile duct cancer. Research has shown that patients with pancreatic cancer who have higher levels of CA 19-9 tend to have more advanced disease.
Non malignant conditions that may elevate CA 19-9 levels include gallstones, pancreatitis, cirrhosis of the liver, and cholecystitis.
CA 15-3 levels are most useful in following the course of treatment in women with diagnosed breast cancer. Cancers of the ovary, lung, and prostate may also raise CA 15-3 levels.
Non malignant conditions that may elevate CA 15-3 include benign breast or ovarian disease, endometriosis, pelvic inflammatory disease, and hepatitis. Pregnancy and lactation can also cause CA 15-3 levels to rise.
NSE has been detected in patients with neuroblastoma, small cell lung cancer, Wilms' tumour, melanoma, and cancers of the thyroid, kidney, testicle, and pancreas. Studies of NSE as a tumour marker have concentrated primarily on patients with neuroblastoma and small cell lung cancer.
Lactate Dehydrogenase (LDH)
LDH was one of the first tumour markers to be introduced into clinical practice since nearly every type of cancer can cause elevations. However, it is also raised in many other diseases. It is currently only used in the monitoring of some lymphomas and leukemias.