What are tumor markers?
A tumor marker is a substance in cancer cells or other cells of the body that is present or occurs in response to cancer or some conditions Benignas (not cancerous). The tumor marker offers information about cancer, such as the degree of malignancy, if possible use Directed therapy or if the cancer responds to the treatment,
In general, the tumor markers that were used were proteins or other substances that both normal and cancer cells produce, but cancer cells produce in greater quantity. These substances are in the blood, urine, the Fecal matter , tumors or other tissues or body liquids of some patients with cancer. However, at present, genomic markers, such as gene mutations, the patterns of Expression of a gene in tumors, and changes that are not genetic in deoxyribonucleic acid (DNA) of a tumor, are used more and more as tumor markers.
The characteristics of many tumor markers that are already used in medicine have been determined. Some are related to a single type of cancer, while others relate to two or more types of cancer. A tumor marker & ldquo; Universal “ that indicates the presence of any type of cancer.
How are tumor markers used in cancer treatment?
There are two main types of tumor markers for different uses in the treatment of cancer: circulating tumor markers and markers in tumor tissues.
Circulating tumor markers: are found in blood, urine, fecal matter or other liquids of the body of some patients with cancer. Circulating tumor markers are used for the following purposes:
- Calculate the forecast
- Detect cancer that remains after treatment ( residual disease ) or that it returns after treatment
- Evaluate a patient's response to treatment
- Monitor a cancer to know if there is resistance to treatment
Although a high concentration of a tumor marker may indicate the presence of cancer, this alone is not enough to diagnose cancer. For example, non-cancerous conditions sometimes produce an increase in concentrations of some tumor markers. In addition, not all people with a type of cancer in particular will have a high concentration of a tumor marker related to that cancer. Therefore, the measurements of circulating tumor markers are usually combined with the results of other tests that are used to diagnose cancer, such as the Biopsias or image obtaining techniques.
Tumor markers are also measured periodically during cancer treatment. For example, if you lower the concentration of a circulating tumor marker, it may indicate that cancer responds to treatment; But if it increases or does not change, it may indicate that the treatment is not working.
Circulating tumor markers are also measured after finishing the treatment to determine if cancer recurred (returned).
Some examples of the most common circulating tumor markers are the following: Calcitonin (by blood test) To evaluate the response to treatment, detect whether the cancer recidated and calculating the forecast of the Medulat thyroid cancer ; CA-125 (through Blood analysis) To evaluate whether cancer treatments work and whether ovarian cancer recurred; microglobulin beta-2 ( Through blood test, urine or cerebrospinal fluid ) To calculate the prognosis and follow the response to the treatment of multiple myeloma, chronic lymphocytic leukemia and some lymphomas.
Tumor markers in tissue: are found in tumors, in general in a sample of the tumor that is taken out during a biopsy. Tumor tumor markers are used for the following purposes:
- Diagnose, Stay Or classify cancer
- Calculate the forecast
- Choose the proper treatment (for example, treatment with Directed Therapy )
In some types of cancer, the concentration of a tumor marker reflects the stadium (extension) of the disease and the prognosis of the patient (probable result or evolution of the disease). For example, the AlfaphetopRotein It is measured in the blood to evaluate the stadium, calculate the prognosis and follow the response to the treatment of the Germinative Cell Tumors . For more information about cancer staging, see page Cancer staging .
Tumor markers are measured before treatment to help doctors plan adequate therapies. Some tests, which are called Diagnostic tests for therapeutic purposes , they are created at the same time as a directed therapy medication and accompany it to determine if treatment with directed therapy is effective. In some cases the tests measure the amount of tumor marker present; In others, the presence of a specific marker is detected, as a mutation in a gene.
There are therapies that are directed to some of these tumor markers in tissue. However, not all sites where directed therapies are pointed out are tumor markers that are tested in patients. For more information about designed therapies to interfere with certain sites that participate in the multiplication and survival of cancer cells, see the fact sheet Therapies directed against cancer .
Some examples of the most common tumor markers are the following: estrogen receiver and Progesterone receiver (breast cancer) to determine if the hormonal therapy and some directed therapies are adequate; Analysis of the mutation at the Gen EGFR < / a> (non-small cell lung cancer) to determine treatment and prognosis; PD-L1 (many types of cancer) to evaluate if the use of therapy directed with Inhibitors of immune control points is adequate.
How are tumor markers measured?
The doctor extracts a sample of tumor tissue or liquid from the body and sends it to a laboratory where several methods are used to measure the concentration or presence (or absence) of the tumor marker.
If the tumor marker is used to check if the treatment is effective or if the cancer recurred (returned), the marker's concentration is measured in several samples that are extracted at different times during treatment and after it. In general, these series measurements allow us to observe the changes in the concentration of the marker over time and are more useful than a single measurement.
Other markers do not change over time and indicate the presence or absence of a certain genetic alteration, which helps identify a possible Directed therapy for the tumor. However, the proportion of tumor cells with alteration may change during treatment and after it.
Does the National Cancer Institute offer guidelines for the use of tumor markers?
The National Cancer Institute (NCI) does not offer guidelines for the use of tumor markers. However, several national and international organizations have guidelines for the use of tumor markers for some types of cancer:
What are the tumor markers that are used now and what types of cancer?
At present, there are several tumor markers that are used for different types of cancer. For more information, see the list of Tumor markers for common use . Although most marker tests are analyzed in laboratories that meet the standards established by the Amendments for the improvement of clinical laboratories (CLIA) , others can not be done and therefore are considered experimental.
Is it possible to use tumor markers to detect cancer?
Because tumor markers serve to predict the Answer of a tumor to treatment and do Forecasts , the researchers had the hope that they could be used in the early detection tests of cancer, before the appearance of symptoms.
However, although tumor markers are very useful in determining whether a tumor responds to treatment or evaluating if there is a recurrence, no tumor marker identified to date presents sensitivity (ie, which identifies correctly those who have the disease ) No specificity (that is, it identifies correctly those who do not have the disease) sufficient to detect cancer.
For example, until recently, the Specific prostate antigen test ( PSA ), which measures the concentration of the PSA in the blood, was used as a routine test to detect prostate cancer. But the high concentration of the PSA can produce both a non-cancerous prostate condition ( benign ) like prostate cancer, and most men who have a high concentration of PSA do not have prostate cancer. In the results of the data-glossary-id="cdr0000044195" href="https://www.cancer.gov/common/popups/popdefinition.aspx?id=CDR0000044195&version=Patient&language=en"> Clinical studies it was observed that PSA tests, at best, only decrease the number of prostate cancer deaths and may take the Obrediagnosis and overweight of the disease. For this reason, the PSA test is no longer recommended as a routine detection test. Now it is used especially in men with a history of prostate cancer to watch if cancer returned. For more information, see the fact sheet PSA test .
What research is in progress to create more accurate tumor markers?
Nowadays, cancer researchers study protein structure, function and patterns ( Proteomics ), in addition to integrating these studies with the genomics and the analysis of the Expression of a gene or the transcriptomics (this is called proteogenomi CA ) Hopefully to create Biomarkers novels that allow cancer to identify cancer in early stadiums, determine the effectiveness of treatment and the probability that cancer recidive .
Las data-glossary-id="cdr0000779095" href="https://www.cancer.gov/common/popups/popdefinition.aspx?id=CDR0000779095&version=patient&language=en"> Liquid Biopsies They are a new way of studying tumors. New biomarkers may be obtained by studying small pieces of tumor material (even deoxyribonucleic acid [DNA] and other entire molecules and cells) that result from tumors for their analysis in body liquids, such as blood or the urine. In May 2019, the Food and Drug Administration ( FDA ) approved a liquid biopsy test called Cobas® EGFR Mutation Test to detect mutations in the EGFR gene in the circulating DNA of the tumors of patients with lung cancer. At this time, the FDA granted priority to the revision of several new liquid biopsy tests (such as Foundation One® Liquid, GARDANT360®, Signatera ™) that have discovery designation for accelerated approval.
For more information about the NCI function in research support for new cancer diagnostic tools and methods, see page Diagnostic research of cancer .
