Tumor markers: Effective as a complement to other medical tests

When there are cancer cells, the presence of these substances, most of them proteins, can be elevated in blood, urine, feces, tissues … and detected with clinical analysis. Some tumor markers are associated with a single tumor and others with several.

For the Spanish Society of Medical Oncology ( SEOM ), through its scientific secretary oncologist Guillermo de Velasco, “tumor markers are not determinative by themselves to give a diagnosis, but they become complementary tests that help to know better what is the diagnosis and the situation of the disease?

For this doctor of the Oncology Service at the Hospital 12 de Octubre in Madrid, “before asking for a marker, we must assess the context in which it is requested and if it turns out to be positive, what value it adds”.

For his part, Dr. Fabricio Racca, oncologist of the Unit of Breast and Genitourinary Tumors of the IOB Institute of Oncology of Barcelona, ​​considers: “If we ask for a battery of studies among them, tumor markers, in an asymptomatic patient and without a high suspicion of a neoplastic disease, not only do they have no diagnostic benefit, but we can also obtain a false positive that far from obtaining an early diagnosis, generates a new uncertainty in the doctor and unnecessary distress in the patient “.

In the opinion of this specialist, “tumor markers are a tool of importance in patients with high suspicion or already diagnosed with cancer, and therefore, may be useful to assess the evolution of the disease and the response to some treatments.”

But, precise, it is a tool more “with which we have doctors to study neoplastic disease, but it does not represent a criterion of certainty or a reliable criterion” by itself, unlike tissue samples obtained by a biopsy or a surgical sample, with the help of, for example, a high-sensitivity imaging study.

“The tumor markers are not really determinant to make a diagnosis, and should not be used in a standardized manner in asymptomatic patients. Conversely, the marker acquires another relevance in patients with symptoms and the presence of imaging tests that make us have a high suspicion of a tumor disease. Therefore, and as usual in medical practice, the diagnosis must be completed with a tissue biopsy, “argues the IOB doctor.

Carcinoembryonic antigen (CEA) and prostate-specific antigen (PSA), in colorectal and prostate cancer , respectively, are the most requested tumor markers by primary care physicians and by some medical specialists in hospitals. asymptomatic patients.

According to this oncologist, one of the possible reasons for requesting a large number of these studies is the fact that it is a quick method, easy to extract (a blood sample) and relatively inexpensive compared to other studies. .

“But we must not forget,” he adds, “if these results have a real impact on early diagnosis and, therefore, on the prognosis of the disease.”

False positives

According to the National Cancer Institute of the United States, “no tumor marker that has been identified so far is sufficiently sensitive or specific to be used on its own as a cancer screening test”.

Tumor markers
Doctor Fabricio Racca, oncologist of the Breast and Genitourinary Tumors Unit of the IOB Institute of Oncology of Barcelona. Photo IOB.

And one of the reasons is the risk of false positives since these proteins can be raised in the body without responding to the presence of a tumor.

An example is the CEA marker that can be increased by breast, colon or other less frequent tumors, but it also rises in smoking patients.

Dr. Racca explains: “Proteins are very dynamic substances. They are metabolized, degraded and eliminated by different causes and may be abnormally elevated by a hyperdynamic stage of the body or, for example, by physiological conditions or non-tumor diseases. “

These are the cases of possible elevation of PSA in patients with benign prostatic hyperplasia (“large prostate”), CEA in some intestinal inflammatory diseases or elevation of CA-125 in the case of patients with ascites (liquid in the peritoneal cavity) or presence of pleural effusion, he mentions.

It is true that when the disease is more advanced, tumor markers are usually elevated, he says.

“Now, in some malignant diseases, when they are in a period of early development, the marker can have a value within normal parameters and if I want to have an early diagnosis … So, what value does that marker have? Therefore, in my opinion we should always request these studies, accompanied by other complementary methods that increase the effectiveness of the diagnosis in an appropriate situation of clinical suspicion, “says the doctor.

Most common tumor markers

According to the classification of the National Cancer Institute of the United States, these are some of the most frequent tumor markers:

C- plantar antigen (CEA)

  • Types of cancer: Colorectal cancer and other cancers

  • Analyzed tissue: Blood

  • Utility: To monitor if cancer treatments work well or check if the cancer has returned

Benign prostatic antigen 
or esp ecífico (PSA)

  • Type of cancer: Prostate cancer

  • Analyzed tissue: Blood

  • Utility: To aid in the diagnosis , evaluate the reaction to treatment and seek recurrence or relapse.

CA15-3 / CA27.29

  • Type of cancer: Breast cancer

  • Analyzed tissue: Blood

  • Utility: To assess if the treatment is working or if the disease has returned.


  • Cancers: pancreatic cancer , gallbladder cancer , bi duct cancer rolling and cancer g astrico .

  • Analyzed tissue: Blood

  • Utility: To assess if the treatment is working


  • Cancer: Cancer ovaries

  • Analyzed tissue: Blood

  • Usefulness: To help in the diagnosis, in the evaluation of the reaction to treatment and in the evaluation of recurrence

Chorionic gonadotrophin hum ana ß (Beta-hCG)

  • Cancers: Coriocarcin oma and germ cell tumors

  • Tissue analyzed: Urine or blood

  • Utility: To evaluate the stage, the prognosis and the reaction to treatment

Alpha-fetoprotein (AFP)

  • Cancers: Cancer Liver liver and germ cell tumors

  • Analyzed tissue: Blood

  • Utility: To help DIAGNO Sticar the liver cancer and igilar response to treatment; to assess the stage , the pron Not unexpectedly , and response to treatment of germ cell tumors.

Tumor markers
Pipes with organic samples to analyze. Photo courtesy of IOB

The therapeutic targets

Also the genetic alterations of the tumor or of the germinal line of the patient have changed the clinical practice of oncology in the last decades.

These are genetic mutations that can predispose to cancer and, in some cases, may be hereditary, such as the BRCA1 and BRCA2 genes , whose alteration can lead to the development of breast and ovarian cancer. There are cases in which these neoplastic diseases can be prevented with preventive surgeries , in the context of an adequate study and always under medical advice.

This is the case of the presence of an overexpression of a protein called HER2, present in some breast cancers or gastric cancer; or mutations of EGFR or ALK in lung cancer or the presence of the Philadelphia chromosome in some types of leukemia.

“Molecular genetic studies today, usually, are performed in a patient with a diagnosis of a tumor to which we want to perform a treatment” directed “to a specific mutation or molecular alteration, either in standard treatment or in clinical trial protocols. , and in some cases, prevent a second tumor, as in the cases of BRCA1 and BRCA2 mutations, in the breast or ovaries, “says the IOB doctor.

In current research, along with other objectives, is the study and development of response biomarkers, which will allow us to identify and treat different types of cancer in a more precise and less harmful for the patient.

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