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Why Tumor Markers Are Important

Tumor markers have assumed an increasingly important role in the detection, diagnosis, treatment, and monitoring of some types of cancer.

How they will be used

Tumor markers can be used for several purposes:
  • Screening a healthy population or a high-risk population for the presence of cancer
  • Making an early diagnosis of a specific type of cancer
  • Determining the prognosis for a patient
  • Monitoring a patient in remission or while having surgery, radiation, or chemotherapy.

No test meets all of these requirements yet. Specifically, no marker has been established as a practical cancer-screening tool, either in a general healthy population or in most high-risk populations.

The reason for this is the relative lack of sensitivity and specificity of the available tests, given the low prevalence of cancers in most population groups but work continues to find better biomarkers.


This image depicts a newly-developed chip that can identify four different biomarkers for colon cancer.

This is still at the development phase but demonstrates the future for better biomarker detection.

Image courtesy of The Next Big Future      

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How are tumor markers classified?

Tumor markers can be classified into two groups: Cancer-specific markers and tissue-specific markers.

Cancer-specific markers

Cancer-specific markers are related to the presence of certain cancers (the tumor itself produces the biomarker). Because there is a large overlap between the many different tumor types and the markers produced, these markers might not be specific enough to make a correct diagnosis.

They can, however, be useful in the follow-up of treated patients to track the progress of the disease or response to treatment. A few examples of these markers are CEA, CA19-9, and CA125 (see the section on "Examples of Tumor Markers" for more information).

Tissue-specific markers

Tissue-specific markers are associated with specific tissues, i.e., the body makes the biomarker in response to the presence of cancer. Generally speaking, these substances are usually not exclusive to the tumor, but may also be elevated in the presence of cancer. But unlike the cancer-specific markers, elevated levels point to a specific tissue having a problem. An example is PSA where it can be elevated when the prostate tissue has problems - sometimes this may be cancer, sometimes not.

How tumor markers are identified

Many tumor markers are proteins. Therefore, many tumor markers are identified through tests that evaluate specific proteins in the body associated with cancer or non-cancerous conditions.

Proteins are identified through the help of a branch of science called proteomics, which is the study of all proteins in a cell, tissue, or organism, including the shape, function, and patterns of expression.

Cancer proteomics, or the study of proteins associated with cancer, enables mapping of proteins involved when normal cellular pathways support malignant growth. In cancerous tissue, some of the proteins critical for normal communication are damaged, inactive, overactive, or missing entirely.

The full set of proteins disrupting cellular communications may vary from one cancer type to another, and possibly from one patient to another within a cancer type.

The challenge for cancer detection and diagnosis is to locate the renegade genes and proteins (the defective, and dominating molecules) that disrupt communication in once normal cells.


This requires opening the cell and analyzing the biomolecules inside. The earlier this detection and diagnosis can occur, the better.


Image courtesy of The National Cancer Institute


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