A tumor marker is a substance present in the body. When its dosage is high, it may reveal cancer. There are markers for different cancers (colon, liver, blood, lung, pancreas, ovary, testicles…). What are the different markers of cancer?

Definition: what is a cancer marker?

A tumor marker is a substance (protein, hormone) naturally present in the body, which in case of high dosage, can indicate the presence of cancer. But it can also be made by the body when a tumor grows, or by the cancer cells themselves. Tumor markers can be specific to certain cancers, or common to different cancers. Important : the dosage of certain tumor markers can be high without systematic demonstration of an underlying cancerous condition. The dosage of tumor markers can be useful at different stages of cancer care : for its screening, its diagnosis, the determination of its stage (propagation) or its prognosis (aggressiveness of the tumour). It is also useful for choosing and monitoring the treatment, evaluating its effectiveness (response) or even estimating the risk of recurrence.

What are the markers of cancer?

► Blood test for alpha-fetoprotein (AFP) can help diagnose and monitor the response to treatment of different cancers: primary liver cancer, testicular cancer, ovarian cancer.

► CA 125 blood test (tumour antigen 125) is prescribed for the follow-up of ovarian cancers in order to check the response to treatment and detect a recurrence after treatment. It may also be prescribed if a patient has signs suggestive of another cancerous condition.

► CA 15-3 antigen (tumor antigen 15-3) is a fairly specific marker for breast cancer. Its rate can nevertheless be increased in the presence of other cancers: ovarian, liver and sometimes lung cancers. The CA 15-3 blood assay is generally carried out to verify the therapeutic efficacy of the treatment of breast cancer, or to detect a recurrence after the implementation of the treatment.

► The determination of CA 19-9 (carbohydrate antigen 19-9) is indicated to evaluate the response to treatment of pancreatic cancer (at an advanced stage), or if it has come back after treatment, thus indicating a recurrence.

► CEA (carcinoembryonic antigen) assay is primarily prescribed to aid in the diagnosis of colorectal cancer and to monitor response to treatment. The value of its dosage is also considered as a prognostic factor for the disease. It may also be indicated to establish the prognosis of patients with various cancers, such as breast and lung cancer.

► Human Chorionic Gonadotropin (HCG or BHCG) in the diagnosis of genital cancers. This hormone is produced naturally by the placenta during pregnancy. It is also made by some cancer cells. The dosage of human chorionic gonadotropin (HCG or BHCG) is involved in the diagnosis of certain cancers, in particular for testicular cancer, ovarian cancer (germ cell tumor), and a certain type of cancer of the uterus. It also helps to assess the therapeutic effectiveness of the treatment.

► Prostate Specific Antigen (PAS) is a protein naturally made by prostate cells. A blood test measures the amount of PSA in the blood. It is useful for screening for prostate cancer in the presence of risk factors (age, history) or suggestive symptoms. It is also of interest for evaluating the effectiveness of the treatment and monitoring a possible recurrence. Note that only 1 in 4 men with abnormal PAS levels develop prostate cancer.

What do elevated tumor markers mean?

From the moment a cancerous cell grows, it will multiply and when the tumor grows morphologically, the tumor marker will increase and become elevated. “But a tumor marker alone, isolated, taken individually, is not enough to diagnose cancer. It is only for the thyroid where when you have the tumor marker, it means that you have cancer. Otherwise , all the other markers we have them. It is for this reason that it is not necessarily used in primary diagnosis. It is when we notice that it increases that we will prescribe examinations such as scanner or MRI or even a biopsy and it is all of these elements that will allow us to know if the patient will develop this or that cancer”, reassures Dr François Blanchecotte.

What do low tumor markers mean?

“Tumor markers are present in the body, both in a physiological situation and in a cancerous situation. When we are going to treat cancer, if the tumor regresses, the tumor marker will decrease proportionally and at that time, the marker will serve as indicator of successful treatment. If we find an isolated increase in a protein marker, it does not necessarily mean that we have cancer. Once diagnosed, tumor markers should be used as an aid in monitoring the disease.” explains the specialist.

Thanks to Dr François Blanchecotte, President of the Syndicat des biologists.