Biomarker Testing for Colorectal Cancer



You may need to be tested for certain biomarkers before you receive certain types of chemotherapy treatment. Your results can help your healthcare team determine which drug may or may not be right for you.

Some (not all) chemotherapy drugs will not work if your tumor has a certain genetic mutation.

What’s a Biomarker?

Biomarkers are specific characteristics of cancer cells that can be identified with special tests. These tests can identify whether a specific gene in a cell is mutated.

For example, in colorectal cancer, genes such as KRAS, NRAS and BRAF indicate gene mutations from metastatic cancer. Testing positive for these gene mutations will show your doctors which treatments to avoid.

Vocabulary for Biomarkers

  • Prognostic markers are used to describe a patient’s outcomes, but don’t predict a response to treatment.
  • Predictive biomarkers determine whether or not a patient may respond well to a particular targeted treatment

Common Biomarker Tests for Colon Cancer


Download the Biomarkers Fact Sheet

There are very few biomarkers that have been scientifically shown to be meaningful in colorectal cancer, although research is moving aggressively in this area. Talk with your healthcare team to see if these tests are appropriate for you.

KRAS and NRAS testing

KRAS and NRAS are genes that play an important role in instructing colorectal cancer cells to grow and divide as part of the epidermal growth factor receptor (EGFR) process. If a biomarker test indicates a KRAS or an NRAS mutation, then drugs that target EGFR may not benefit that patient. This test is typically for stage IV patients, and sometimes for stage III recurrence.

*All stage IV patients need to undergo KRAS biomarker testing before beginning treatment.

See all of our information about KRAS testing.


BRAF testing

BRAF is also a gene that signals cells to divide. Patients with mutant BRAF genes do not respond to EGFR-targeting drugs, and generally have a poorer prognosis. Like KRAS and NRAS testing, this test is typically for stage IV patients only, although sometimes with stage III recurrence.

See all of our information about BRAF testing. 


Carcinoembryonic antigen (CEA)

CEA is a protein that may be higher in colorectal cancer patients. High levels of CEA may indicate that cancer is growing while low levels may indicate that treatment is working.

 See all of our information about CEA.


Content medically-reviewed by members of the Fight Colorectal Cancer Medical Advisory Board, February 2014

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