Biomarker testing and genetic testing have different purposes in diagnosing colorectal cancer. The first helps doctors understand cancer’s growth and spread, while the second assesses a person’s inherited risk.

Colorectal cancer (CRC) starts in the colon or rectum of the large intestine. It’s sometimes referred to as “colon cancer” or “rectal cancer,” depending on the area it first develops.

According to the American Cancer Society, more than 150,000 new cases of colorectal cancer are expected in 2025. It’s one of the top causes of cancer-related death, while the overall risk of developing CRC for people assigned male at birth is about 1 in 24, and 1 in 26 for those assigned female at birth.

Despite being one of the most common cancers globally, survival rates for CRC have improved in many parts of the world due to medical advancements in biomarker testing and genetic testing.

Both biomarker testing and genetic testing in CRC involve screening for genetic mutations, but these tests have distinct purposes during the diagnosis process.

You’ll notice that the language used to share stats and other data points is pretty binary, fluctuating between the use of “male” and “female” or “men” and “women.”

Although we typically avoid language like this, specificity is key when reporting on research participants and clinical findings.

The studies and surveys referenced in this article didn’t report data on or include participants who were transgender, nonbinary, gender nonconforming, genderqueer, agender, or genderless.

Biomarker testing in medicine is used to assess, predict, or monitor disease progression.

Biomarkers (biological markers) are measurable biological processes, molecules, and cellular changes that provide insight into what’s happening in your body at an exact moment. The presence or absence of biomarkers or their changes provides important insight into a developing or progressing medical condition.

In CRC, biomarker testing, also called “tumor testing,” is performed on cancer cells to look for tumor-specific changes. It detects the presence of acquired genetic mutations (somatic mutations), cellular changes, and DNA changes in cancer that could influence its growth and spread. CRC biomarkers can relay information about your overall outlook and whether CRC may be responsive to certain treatments more than others.

Genetic testing is a specific type of biomarker testing that analyzes your DNA to determine your risk of cancer.

In CRC, genetic testing looks for inherited genetic mutations or variants (called germline mutations) associated with an increased risk of CRC.

Genetic testing is mainly used as a form of risk assessment. Doctors perform these tests if you have a family history of CRC or meet the criteria for an inherited cancer syndrome.

If you’ve received a diagnosis of CRC and didn’t undergo genetic testing first, your doctor may still recommend testing after a diagnosis in certain instances. These include when there’s a family history of CRC or if the disease appears to follow a hereditary pattern of development.

There are several types of tests doctors run when assessing biomarkers and genetic risk in CRC, including:

  • Single gene: This looks for an isolated gene.
  • Panel test: This screens multiple genes at once.
  • Whole-genome sequencing: This assesses all the DNA in a cell.
  • Whole-exome sequencing: This screens only the components in a gene responsible for protein coding.
  • Tumor-mutational burden: This determines the overall number of genetic changes in a tumor’s DNA.

Common tumor biomarkers

Biomarker testing in CRC screens for various measurable tumor indicators, including genetic mutations, protein expression levels, signaling molecules, DNA sequencing patterns, antigens, and more. Common CRC tumor biomarkers your doctor may test for include:

  • MSI-H/dMMR
  • sidedness (which side of the colon the cancer is located on)
  • KRAS
  • NRAS
  • BRAF
  • HER2
  • EGFR
  • CEA
  • TRK fusions
  • DPD
  • ctDNA
  • PD-L1 pathway
  • WNT pathway
  • RET
  • VEGF
  • CTC
  • MMR deficiency

Common genetic tests

Genetic testing for CRC typically includes screening for genetic mutations relating to inherited cancer syndromes such as:

  • Lynch syndrome
  • familial adenomatous polyposis (FAP)
  • MUTYH-associated polyposis
  • Peutz-Jeghers syndrome

These are inherited conditions that significantly increase your risk of developing CRC.

Genes that may be screened in genetic testing for CRC risk include:

  • MLH1
  • MSH2
  • MSH3
  • MSH6
  • PMS2
  • APC
  • MUTYH
  • POLE
  • POLD1
  • NTHL1
  • GREM1
  • RNF43 (primarily used in research)
  • RPS20 (primarily used in research)

Genetic testing and biomarker testing in CRC are part of precision medicine and can help improve your cancer outcomes.

Genetic testing before a potential cancer diagnosis allows you and your doctor to understand your individual risk for CRC. Knowing your likelihood can help you take preventive steps to lower your overall risk of cancer and can help detect cancer in its earliest, most treatable stages.

If you’ve received a CRC diagnosis, biomarker testing reveals details about the disease that help your doctor treat it with the most effective therapies right from the start. Certain biomarkers, for example, can indicate if CRC will be responsive to immunotherapy or monoclonal antibody therapy. Other biomarkers can help predict treatment response and monitor recurrence.

Anyone with a CRC diagnosis is a candidate for biomarker testing to help direct treatment planning, but not everyone requires genetic testing to determine their inherited risk.

Genetic testing is typically recommended when:

  • you have a family history of CRC or a hereditary cancer syndrome in more than one biological relative
  • you received a CRC diagnosis before the age of 50
  • CRC was diagnosed in a first-degree relative younger than age 50
  • multiple family members have received a diagnosis of another type of cancer associated with hereditary cancer syndromes (like ovarian or stomach cancer)
  • you’ve received a diagnosis of two or more primary types of cancer
  • biomarker testing suggests a germline mutation
  • you have a significant number of colorectal polyps

Anyone can develop CRC, so the United States Preventive Services Task Force (USPSTF) recommends screening for all adults ages 45 and over.

However, you don’t have to wait until you are 45 to talk with your doctor about CRC, especially if you have a family history of the condition or inherited cancer syndromes.

To help make the most of this conversation with your doctor, consider these tips:

  • Research CRC and learn as much as you can before your appointment.
  • Talk with your parents and biological family members to verify your family medical history.
  • Bring a written list of questions.
  • Have a friend or loved one come with you for support and another perspective.
  • Take notes on what your doctor says to review at home.

If you’ve already had biomarker testing or genetic testing for CRC, questions that may be helpful to ask your doctor include:

  • Which genes and biomarkers were tested for?
  • Did my tests show any biomarkers or inherited mutations?
  • What do the results of my tests mean for my CRC risk or treatment planning?
  • Were all possible biomarkers tested for? If not, why?
  • Will more genetic or biomarker testing be necessary?

Biomarker testing and genetic testing are part of precision medicine. Genetic testing helps doctors assess your inherited risk for colorectal cancer (CRC), while biomarker testing relays important details about cancer’s characteristics.

Not everyone needs genetic testing for CRC, but anyone with a diagnosis of the disease is a candidate for biomarker testing. Both options can help improve your outcomes if you have CRC.