BiomarkersCancer Screening

What Are Cancer Biomarkers, and Why Are They Important?

Biomarkers are biologic markers that indicate changes in our genes and may increase the risk of cancer.
May 2018 – Cancer Biomarkers and Molecular Testing
Kristen Chanley

Understanding the characteristics of a tumor allows physicians to customize treatment to that cancer. Changes in our genes, RNA, or DNA can affect the way our cells develop, and these changes can lead cells to transform from their normal properties and develop into cancer cells. Biomarkers are biological markers that describe changes in our genes, RNA, or DNA.

Biomarkers in cancer have been defined as molecules produced by the body or by a tumor in response to cancer cells,1 and help to characterize the features of a cancer, as well as influence the cancer response to treatment. Biomarkers, or tumor markers, can help to determine the characteristics of a tumor, the severity or grade of the cancer, as well as the potential benefits of available treatments for that cancer.2

The use of biomarkers in cancer has revolutionized the treatment of many types of cancer and has promoted the use of a personalized approach to the treatment of patients with cancer.3 Cancer biomarkers are identified through gene or molecular testing and can be characterized to paint a specific picture of a tumor.

Tumor Testing for Biomarkers

Testing for tumor biomarkers is done via body tissue samples, blood samples, or other bodily fluids to identify the molecular features of a cancer. Molecular or genetic testing involves testing of genes or DNA in our cells that can identify if a specific biomarker is involved in the cancer. If molecular testing identifies a biomarker in the cancer cells, it helps to characterize the specific nature of the cancer.1

Biomarker testing can be done before the cancer diagnosis, during diagnosis, or after diagnosis, and can save additional testing. For example, according to the National Cancer Institute, results of a recent study show that “testing for two biomarkers in urine may help some men avoid having to undergo unnecessary biopsy to detect a suspected prostate cancer.”4

These 2 RNA biomarkers, called PCA3 and T2:ERG, have been associated with aggressive prostate cancer and can be detected by genomic testing, sparing men necessary tissue biopsies, which are more invasive procedures.

People diagnosed with cancer should ask their doctor about biomarkers, and whether biomarker tests are appropriate for them. Some biomarker tests, such as genetic testing for inherited mutations in breast cancer, are often done as part of the initial diagnosis, but other molecular tests are optional and must be ordered by a doctor.

Depending on the type of cancer and the known biomarkers related to that type of cancer, many molecular or genetic tests may be available today to identify biomarkers often found with that cancer. Understanding the biomarkers related to your cancer may help you to get the best treatment available today.

In fact, many new targeted drugs, as well as immunotherapies, are today approved by the FDA together with a “companion diagnostic,” which is a test that can identify the specific biomarker that the new drug is targeting. When a drug is approved with a related test, patients are often required to have a biomarker test before they can be prescribed that therapy.

Cytogenetic tests. Cytogenetic tests look for structural abnormalities in our chromosomes that may lead to a cancer diagnosis. Chromosomes can be measured through blood cells or other tissues, such as bone marrow. Some cancers are characterized by a specific change (a biomarker) in the chromosome, and this biomarker can aid in screening and diagnosis. For instance, in chronic myeloid leukemia, a change in the Philadelphia chromosome is a common feature (or biomarker) in this type of blood cancer.

Gene tests. Molecular tests of our genes (which are contained inside our chromosomes) look for biomarkers, such as extra copies of a gene (duplicated or amplified genes), missing genes (gene deletions), or incorrectly placed genes (translocated genes). In addition, gene testing can look for changes (mutations) in our genes.

Gene tests are typically performed on small tissue samples, but increasingly, blood tests or “liquid biopsies” may be replacing tissue testing (or a biopsy). A single gene test can look for a specific biomarker, such as HER2 or EGFR; by contrast, gene-expression panels look for several or many biomarkers at the same time.

Biochemical tests. When genes are changed abnormally (mutated), the proteins created by those genes are sometimes abnormal, and often serve as biomarkers. Therefore, instead of using gene tests to identify gene abnormalities, physicians may decide to use a biochemical test to identify abnormal proteins. For example, a test can either look for the HER2 gene or for the HER2 protein. Biochemical tests require a tissue sample in which the protein is present. Other biochemical tests look for the impact of the treatment on the cancer to show whether the cancer is responding to treatment.

Targeted Therapies Focus on Biomarkers

When a biomarker is identified in a cancer through molecular or genetic testing, it tells the physician what makes the cancer grow and thrive, and that information allows physicians to decide what may be the most effective treatment for the patient. Using the information gained from such testing can also help patients to avoid the often frustrating, painful, and costly process of a trial-and-error approach in the search for the best treatment for that patient.

Patients whose tumor has a known biomarker may, therefore, be spared a treatment that would not be useful for them, and instead start treatment with a therapy that is designed to attack the specific biomarker associated with their cancer.

For many biomarkers today, targeted therapies, and increasingly immunotherapies, are available that are designed to fight the specific biomarker that causes the cancer to grow and progress. Unlike standard chemotherapy, targeted therapies attack the cancer cells only, leaving most healthy cells alone, which improves the patient’s quality of life and reduces the drug’s side effects. One example of targeted therapies is the case of non–small-cell lung cancer (NSCLC), the most common type of lung cancer.

About 10% to 15% of patients with NSCLC have the biomarker known as EGFR mutation, and 5% of patients with NSCLC have the biomarker called ALK mutation. These mutations cause the cancer to behave in a different way from NSCLC without those mutations and not respond to therapies that don’t target those mutations.

Reduced side effects. Most cancer treatments carry side effects. When a patient with a cancer biomarker is being treated with a targeted therapy, the patient can be assured that he or she is not receiving a drug that may not really be useful, and that the drug will also have fewer serious side effects than chemotherapy. Starting with the best drug that demonstrated benefits in cancer with that type of biomarker can reduce the use of unhelpful drugs, and spare the patient unnecessary side effects.

For some tumors, using a targeted therapy may also mean a reduction in chemotherapy, which is known to have debilitating side effects such as nausea, vomiting, and hair loss. For example, if all women with breast cancer had genetic testing to look for the biomarker known as BRCA1 or BRCA2 mutation before receiving treatment, the overall use of chemotherapy in patients with breast cancer would decrease by about 34%.5

Lower costs. In addition, when a patient’s treatment is selected based on a biomarker, it can reduce the costs to the patient, by avoiding unnecessary treatments and by having fewer side effects. For example, if all patients with metastatic colorectal cancer had a genetic test to see if their cancer has a biomarker called “KRAS mutation” before receiving treatment, that would reduce the annual costs for patients and for the U.S. healthcare system by about $604,000,000.5 And, when treatment for early-stage breast cancer is selected after patients have the molecular-profiling test Oncotype DX, the cost for the patient is reduced by about $2,256, as a result of less use of chemotherapy.6

The Future of Cancer Biomarkers

Researchers are now focusing on how best to treat cancer based on biomarkers by investigating many biomarkers in clinical trials. The major clinical trials underway based on biomarkers are:

  • NCI-MATCH Trial ( This clinical trial is investigating targeted drugs that are effective in 1 type of cancer with specific biomarkers to see if these drugs are also beneficial in other cancers that have the same biomarkers
  • Lung-MAP ( This biomarker-driven clinical trial tests patients with lung cancer for a biomarker, and then assigns each patient to 1 of several sub-studies, each study testing a different drug to see which of these drugs is best for that biomarker
  • TAPUR Study ( Patients with advanced cancer and related gene mutations are being treated with new targeted therapies to see which drug is best for these mutations.

The increasing use of biomarkers in cancer care is an exciting advance in personalized medicine in cancer and improved outcomes for patients. Researchers are working hard to improve biomarker testing and to understand how the information gained from biomarker testing can be used across all tumor types; this presents a radically new approach to patient care that is focused on personalized care of each individual patient.


1. Füzéry AK, Levin J, Chan MM, Chan DW. Translation of proteomic biomarkers into FDA approved cancer diagnostics: issues and challenges. Clinical Proteomics. 2013;10(1):13.
2. National Cancer Institute. Tumor markers. June 15, 2015.
3. Kamel HFM, Al-Amodi HSAB. Exploitation of gene expression and cancer biomarkers in paving the path to era of personalized medicine. Genomics, Proteomics & Bioinformatics. 2017;15(4):220-235.
4. National Cancer Institute. Biomarker test could reduce unnecessary biopsies to detect prostate cancer. June 9, 2017.
5. Personalized Medicine Coalition. By the numbers. 2014.
6. Lyman GH, Cosler LE, Kuderer NM, Hornberger J. Impact of a 21-gene RT-PCR assay on treatment decisions in early-stage breast cancer: an economic analysis based on prognostic and predictive validation studies. Cancer. 2007;109(6):1011-1018.

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Last modified: June 20, 2018

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