What are tumor markers?
Tumor markers (“cancer markers”) are biochemical substances that can occur in elevated amounts in the body in some types of cancer. They are either produced by the tumor cells themselves or are produced in increased amounts because the tumor stimulates their production in the body’s own cells. However, benign diseases can also cause an increase in tumor markers.
What are tumor markers made of?
Tumor markers are often composed of sugars and proteins (so-called glycoproteins). One example is carcinoembryonic antigen (CEA for short), which consists of 50 to 60 percent carbohydrates and rises in cases of colon cancer, among others.
A tumor marker can also be an enzyme or hormone. An enzymatic tumor marker, for example, is the neuron-specific enolase, while a hormonal tumor marker is the thyroid hormone calcitonin.
Genes as “tumor markers
At the same time, the expression of certain gene markers in the tumor cells can indicate that a cancer can be successfully treated with a particular therapy. In this case, the drug used is directed against a specific structure of the cancer cells. Doctors refer to this as “targeted therapy”. For example, HER2-positive tumors can be treated with the active substance trastuzumab.
When are tumor markers determined?
The doctor therefore usually only determines the tumor markers if the cancer is already known, in order to monitor its progress and assess the success or failure of cancer therapy (such as chemotherapy or radiation therapy): If previously elevated values decrease, the patient responds well to the therapy. If, on the other hand, the tumor marker values remain elevated or even rise, the previous therapy is obviously not very successful.
Which tumor marker values are normal?
The most important tumor markers: overview
|
Designation |
Tumor marker standard value |
Possible indicator of… |
Note |
|
AFP (alpha-fetoprotein) |
20 ng/ml |
Liver cell cancer (hepatocellular carcinoma), germ cell tumors (benign and malignant growths of the ovaries and testes) |
Also tested in prenatal diagnosis when asking about Down syndrome or neural tube defects; also elevated in inflammatory liver disease. |
|
Beta-HCG |
10 U/l (serum) for non-pregnant women and men; 20 U/l (urine) |
Germ cell tumors |
|
|
CEA (carcino-embryonic antigen) |
Non-smokers: up to 4.6 ng/ml Smokers: 3.5 – 10.0 ng/ml (25% of cases) > 10.0 ng/ml (1% of cases) > 20.0 ng/ml (V.a. malignant process) |
Adenocarcinomas of the digestive tract (mainly colon cancer), but also bronchial carcinomas |
Also increased in smokers and in people with liver disease. |
|
PSA (prostate specific antigen) |
4 ng/ml (Guidelines of the German Urologists) |
Prostate cancer |
Also increases after prostate irritation or benign prostate enlargement. |
|
Ovarian Cancer |
Also increased in pregnancy, pancreatitis, hepatitis, cirrhosis of the liver as well as endometriosis. |
||
|
< 31 U/ml |
Breast cancer and ovarian cancer |
||
|
< 37 U/ml |
Cancers of the digestive tract, pancreas or bile ducts |
Also elevated in bacterial bile duct inflammation, alcohol abuse, or primary biliary cirrhosis. |
|
|
up to 4.6 U/ml |
Ovarian cancer, gastric cancer |
Also increased in inflammation of female reproductive organs or digestive tract. |
|
|
Calcitonin |
Men: Females: 4.6 ng/l |
Medullary thyroid carcinoma, pancreatic cancer (pancreatic carcinoma), pheochromocytoma |
Also elevated in renal failure, Hashimoto’s thyroiditis, and pregnancy. |
|
CgA (Chromogranin A) |
19 – 98 ng/ml |
Medullary thyroid carcinoma, neuroendocrine tumors, pheochromocytoma |
The range of normal values given is method and age dependent. |
|
< 3.0 ng/ml |
Bronchial carcinoma, bladder cancer (urinary bladder carcinoma) |
Very rarely also increased in benign lung diseases. |
|
|
NSE tumor marker |
Adults: 12.5 µg/l Children < 1 year: 25.0 µg/l |
Small cell lung cancer, neuroendocrine tumors, and neuroblastoma. |
Also elevated in lung diseases (such as fibrosis), meningitis, red blood cell decay, and brain damage due to oxygen deprivation. |
|
Protein S100 |
in serum: Women up to 0.1µg/l Men up to 0.1 µg/l in cerebrospinal fluid: Women up to 2.5 µg/l Men up to 3.4 µg/l |
Black skin cancer (malignant melanoma) |
Also elevated in vascular damage, traumatic brain injury, and liver and kidney failure. |
|
< 5 µg/l |
Squamous cell carcinomas, for example of the lung, esophagus or cervix |
Also elevated in psoriasis, eczema, liver cirrhosis, pancreatitis and tuberculosis. |
Further information: CEA
Read more about this tumor marker in the article CEA.
Further information: CA 15-3
When the determination of CA 15-3 makes sense, read the article CA 15-3.
Further information: CA 19-9
Further information: CA 125
You can find out everything important about this tumor marker in the article CA 125.
When are tumor markers low?
Since the normal values for tumor markers are not defined as reference ranges but as upper limit values, one cannot speak of tumor markers that are too low. However, a drop in tumor markers below previously measured values is usually a good sign: It can indicate the decline of the disease and the effectiveness of a therapy.
If they exceed their threshold value, the tumor markers are elevated. This can be caused by malignant tumor diseases (cancer). There are also different tumor markers for different cancers:
- Breast cancer (mammary carcinoma): CA 15-3, CEA, CA 125
- Ovarian cancer (ovarian carcinoma): CA 125, beta-HCG, AFP
- Lung cancer (lung carcinoma): NSE, CYFRA 21-1, SCC
- Gastric cancer (gastric carcinoma): CEA, CA 72-4, CA 19-9
- Colon cancer (colon carcinoma): CEA
- Prostate cancer (prostate carcinoma): PSA
- etc.
Apart from that, some tumor markers are also elevated in non-cancer related diseases. For example, protein S100 is elevated in skin cancer (melanoma) on the one hand, and in liver failure and traumatic brain injury on the other.
Tumor markers in pregnancy
What to do in case of altered tumor markers?
Moreover, for most tumor markers there is no fixed upper limit above which a carcinoma is certain. This also applies vice versa: a low tumor marker does not automatically mean that there is no cancer.
Accordingly, the physician can only assess the test result in conjunction with other findings (for example, ultrasound or CT findings, the patient’s symptoms, results of a gastroscopy and colonoscopy, etc.).
What do altered tumor markers mean in the course of a cancer disease?
If a patient with a known cancer receives therapy (for example, surgery, chemotherapy, radiation therapy or immunotherapy), the doctor often determines the tumor markers again after a few weeks. He compares the current values with those obtained at the time of the initial diagnosis. If the values fall, this is usually a good sign: The patient seems to be responding well to the therapy.