KRAS and Lung Cancer

When tumor tissue is looked at under a microscope, physicians can see what type of cancer it is. But physicians can also look for changes in the DNA of the tumor that might be causing the tumor to grow. Sometimes these changes are called biomarkers or molecular markers.

One way to think about it is that our DNA is like an instruction manual. If there is a typo in the instruction manual, the cell receives wrong instructions and can grow into cancer. Biomarker testing looks for those typos, so physicians know if you are a candidate to receive a targeted therapy that directly addresses those typos. 

An error in the KRAS gene (pronounced K-raz) is one biomarker that physicians look for in non-small cell lung cancer. If you have non-small cell lung cancer, it is important to talk to your doctor about comprehensive biomarker testing to see if you have an error in the KRAS gene or another biomarker. The results of this testing influence your treatment options. To learn more about biomarker testing, visit Lung.org/biomarker-testing. 

What is the KRAS mutation?

The KRAS mutation is an error in a protein in normal cells. It is called KRAS because it was first identified as causing cancer in Kirsten RAt Sarcoma virus. Normally KRAS serves as an information hub for signals in the cell that lead to cell growth. When there is a mutation in KRAS, it signals too much and cells grow without being told to, which causes cancer.

Who is most likely to have a KRAS mutation?

KRAS tends occur more in patients of Western European descent and current or former smokers, but KRAS mutations have been found in people of all different backgrounds. About 20-25% of lung cancer patients have some kind of KRAS mutation.

How do you know if you have a KRAS mutation?

In general, there are two ways to detect KRAS mutations. The best way is through comprehensive next-generation sequencing (NGS). This type of testing places tissue from a patient’s tumor (gathered from a biopsy) in a machine that looks for a large number of possible biomarkers at one time. There may be some situations where a patient can’t undergo the biopsy needed to perform NGS, and so liquid biopsy is recommended. A liquid biopsy can look for certain biomarkers in a patient’s blood. Talk to your doctor to make sure one of these tests was performed.  

Learn more about the different types of biomarker tests here.

Are there different types of KRAS mutations?

There are multiple types of KRAS mutations. About half of patients with a KRAS mutation have what is called a KRAS G12C mutation. The other types of KRAS mutations show up in the other half of patients. 

What is the course of treatment like for someone with a KRAS mutation?

Right now, whether or not a lung cancer patient has a KRAS mutation doesn’t change initial treatment decision making. Standard first-line therapy for a patient with KRAS positive lung cancer may be surgery, radiation, chemotherapy, immunotherapy or a combination based on the stage of their cancer. There is now a targeted therapy pill (also called a KRAS inhibitor) for patients with KRAS G12C. If a patient’s cancer stops responding to chemotherapy or immunotherapy (or a combination), they may be able to go on a targeted therapy pill called sotorasib.

Work with your doctor to discuss your goals and options each time you have to make a treatment decision. The three big questions to ask are:

1. What is the goal of this treatment?
2. What are the potential side effects?
3. What other options do I have?

Research is happening at a rapid pace and your doctor should be up to date on the recommendations for your specific type of lung cancer. If you don’t feel comfortable with the answers you are receiving, do not hesitate to seek out a second opinion.