What Is KRAS Positive Lung Cancer?

In This Article

KRAS refers to a gene that is mutated in some lung cancers and in some other cancer types. People who are KRAS positive have a mutation in this gene, which makes a protein that is important for cell division and growth. Knowing that you are KRAS positive may give you a little more information about your cancer and the type of treatments that might work best for you.

In the West, KRAS is the most common mutation seen in non-small cell lung cancer, the most common type of lung cancer. KRAS mutations seem to be more common in people who’ve smoked or who have been exposed to asbestos.

In those of European descent, the KRAS mutation is found in about 30% of people who have lung adenocarcinomas and in about 5% of people who have lung squamous cell carcinoma (both subtypes of non-small cell lung cancer).

What Does It Mean to Be KRAS Positive?

KRAS technically stands for “Kirsten rat sarcoma viral oncogene homologue,” but it is almost always abbreviated as “KRAS.” 

KRAS is a gene, part of the information coded in your DNA. It contains the instructions for making a protein called K-Ras. This protein is part of an important signaling pathway called RAS/MAPK. The RAS/MAPK pathway plays important roles in signaling the cell that it is time to grow and divide or time to stop. KRAS acts as an important regulatory point in that pathway.

If part of the DNA in one of your cells is damaged, it can cause a mutation to occur in the KRAS gene. For example, this might occur from exposure to a carcinogen (a DNA damaging agent) like tobacco smoke. This could mean that your DNA in the damaged cell might not be able to make normal KRAS protein. Instead, the KRAS might be turned on all the time, and it might not be able to regulate the growth pathway the way it normally would.

When KRAS is acting abnormally like this, it’s called an “oncogene.” This (and possibly additional genetic changes) might cause a person to develop a cancer, a group of cells that divide and grow more than is normal.

A person who is KRAS positive has a mutation in this specific gene that is contributing to their cancer growth. Most research has shown that people who are KRAS positive tend to have cancer that is more difficult to treat successfully.

KRAS mutations are also sometimes found in other types of cancer. These include pancreatic, colon, endometrial, bile duct, and small intestine cancers.

Other Important Lung Cancer Mutations

Mutations in other genes can also drive the growth of a cancer. In lung cancer, some of the other important driver mutations that can promote cancer growth are:

Usually, though not always, someone with a KRAS mutation in their tumor does not have an EGFR mutation or another major mutation driving the cancer.

Not an Inherited Mutation

Some people get confused when they hear the word mutation. Some mutations are inherited from one’s parents, and these might cause or increase the risk of certain diseases. For example, many people are familiar with the BRCA mutation, which increases the risk of breast cancer and some other cancer types. That’s a hereditary mutation, a type of mutation inherited from one’s parents that increases a person’s risk of getting cancer.

However, KRAS is not like this—it’s an acquired mutation that you don’t have from birth. It’s a mutation just found in the cancer itself, one that might be helping to promote its growth. Cancers with different genetic characteristics (e.g., KRAS positive versus KRAS negative) may tend to respond differently to specific therapies. 

KRAS Testing

The American Society of Oncology says that it may be helpful to check for mutations in KRAS and other genes in people with some types of non-small cell lung cancer. For example, people with advanced lung adenocarcinoma may benefit from testing.

Such testing may also be helpful for people with other types of non-small cell lung cancer (with the exception of the squamous subtype). It may also be useful for people who are young (less than age 50) or who never smoked. It is not helpful for people with small cell lung cancers.

It has been thought that knowing whether a person had a mutation in KRAS might help clinicians make the best treatment decisions. People who have a mutation in KRAS don’t respond well to a group of drugs called tyrosine kinase inhibitors, which include Tagrisso (osimertinib).

In contrast, people with a mutation like EGFR tend to respond better to drugs in this group. So, a clinician might choose a different type of therapy (like chemotherapy) in someone with lung cancer known to be positive for KRAS.

However, it’s not completely clear that KRAS testing provides additional helpful information if a person has already had other types of genetic testing, like tests for EGFR. This is still an evolving area of medicine.

Testing for KRAS may become more important if researchers are eventually successful in developing treatments that work particularly well in people who are KRAS positive.

People with metastatic colon cancer also sometimes benefit from KRAS testing, where it can also help guide therapy decisions.

How Is KRAS Tested?

It’s not usually recommended that a person get KRAS testing on its own. Instead, this test will usually be done at the same time as other genetic tests of a cancer sample, like EGFR, BRAF, and ROS1.

It might also be done after you’ve had some initial genetic tests for your cancer but haven’t yet found a driver mutation. As more targeted therapies become available for cancers with specific mutations, it has become critical to get this information.

Sample Testing

Usually, the KRAS test and other genetic tests have been performed on a sample of the cancerous tissue itself. This requires a lung biopsy procedure. This might be done with the use of a long needle. It also might be obtained during bronchoscopy, in which the sample is obtained by going down through the tubes of the lungs. A sample might also already be available in someone who has already had surgery to remove their cancer.

More recently, newer tests have become available that may be able to test for KRAS using a less invasive blood sample. Talk to your doctor about what options are available in your particular situation.

Treatment for KRAS Positive Lung Cancer

Researchers have developed targeted therapies for some of the genetic drivers of lung cancer. For example, therapies have been developed that work particularly well in people with ALK, EGFR, or ROS1 mutations.

Scientists have tried many different strategies to target lung cancers that are KRAS positive. Unfortunately, researchers have not yet successfully developed therapies that would specifically help treat people positive for the KRAS mutation. Worldwide, lung cancer is the leading cause of cancer death in both men and women, and because so many of these cancers are KRAS positive, such a therapy would be a huge innovation. Clinical trials are ongoing for therapies that might be able to treat people who have KRAS positive lung cancers.

Talk to your doctor if you might be interested in participating in a clinical trial for patients positive for the KRAS mutation. You can also check out clinicaltrials.gov to search for clinical trials being conducted around the world.

Until such targeted therapies become available, people with KRAS positive lung cancers will need to pursue standard treatments such as chemotherapy, radiation, and surgery.

Was this page helpful?
Article Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Tomasini P, Walia P, Labbe C, et al. Targeting the KRAS pathway in non-small cell lung cancerOncologist. 2016;21(12):1450–1460. doi:10.1634/theoncologist.2015-0084

  2. Román M, Baraibar I, López I, et al. KRAS oncogene in non-small cell lung cancer: clinical perspectives on the treatment of an old targetMol Cancer. 2018;17(1):33. doi:10.1186/s12943-018-0789-x

  3. Domagala-Kulawik J. New frontiers for molecular pathologyFront Med (Lausanne). 2019;6:284. doi:10.3389/fmed.2019.00284

  4. Kanwal M, Ding XJ, Cao Y. Familial risk for lung cancerOncol Lett. 2017;13(2):535–542. doi:10.3892/ol.2016.5518

  5. Kalemkerian GP, Narula N, Kennedy EB, et al. Molecular testing guideline for the selection of patients with lung cancer for treatment with targeted tyrosine kinase inhibitors: American Society of Clinical Oncology endorsement of the College of American Pathologists/International Association for the Study of Lung Cancer/Association for Molecular Pathology clinical practice guideline update. J Clin Oncol. 2018;36(9):911-919. doi:10.1200/JCO.2017.76.7293

  6. Lam DC. Clinical testing for molecular targets for personalized treatment in lung cancer. Respirology. 2013;18(2):233-7. doi:10.1111/j.1440-1843.2012.02261.x

  7. Roberts PJ, Stinchcombe TE. KRAS mutation: should we test for it, and does it matter?. J Clin Oncol. 2013;31(8):1112-21. doi:10.1200/JCO.2012.43.0454

  8. Porru M, Pompili L, Caruso C, et al. Targeting KRAS in metastatic colorectal cancer: current strategies and emerging opportunitiesJ Exp Clin Cancer Res. 2018;37(1):57. doi:10.1186/s13046-018-0719-1

  9. Shen H, Che K, Cong L, et al. Diagnostic and prognostic value of blood samples for KRAS mutation identification in lung cancer: a meta-analysisOncotarget. 2017;8(22):36812–36823. doi:10.18632/oncotarget.15972

  10. Torre LA, Bray F, Siegel RL, et al. Global cancer statistics, 2012. CA Cancer J Clin. 2015;65:87-108. doi:10.3322/caac.21262

  11. Zappa C, Mousa SA. Non-small cell lung cancer: current treatment and future advancesTransl Lung Cancer Res. 2016;5(3):288–300. doi:10.21037/tlcr.2016.06.07