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  7. KRAS

KRAS and Lung Cancer

Testing for an error in the KRAS gene helps your doctor understand your lung cancer and recommend treatments that may work better for you.

KRAS at a Glance:

  • An error in the KRAS gene, or KRAS mutation, is one type of lung cancer biomarker.
  • Biomarker testing can help identify treatment options.
  • Targeted treatment is currently only available for KRAS in patients with lung cancer, and specifically for one type of KRAS mutation called a G12C mutation. 
  • You can ask for comprehensive biomarker testing at diagnosis or if treatment stops working.

Frequently Asked Questions about Biomarker Testing

What Is KRAS?

It is called KRAS because it was first identified as causing cancer in Kirsten rat sarcoma virus. The KRAS gene normally acts as a communication hub for signals that lead to cell growth. When a mutation occurs, KRAS sends too many signals, causing uncontrolled cell growth and leading to cancer. 

There are several types of KRAS mutations. 

  • About half of patients with lung cancer who have a KRAS mutation have a KRAS G12C mutation. 
  • The other types of KRAS mutations show up in the other half of patients. 
  • KRAS mutations can also occur with other genetic mutations, like STK11, which are seen in about 10% of lung adenocarcinomas.  

Watch as Dr. Erin Schenk explains what KRAS mutation is in lung cancer (video).

Who is more likely to have a KRAS mutation?

About 25% of all patients with lung cancer have some form of KRAS mutation. KRAS gene mutations are more commonly found in people who currently or have smoked in the past. However, KRAS mutations can also occur in patients with diverse backgrounds.

Why KRAS Biomarker Testing Matters

Biomarker testing matters for KRAS‑positive lung cancer because it directly determines which treatments can work, how the disease behaves, and what options may become available over time. The single most important point: KRAS mutations are not all the same, and knowing the exact subtype (such as G12C) can open the door to targeted therapies that would otherwise be missed.

Biomarker testing looks for specific genetic changes in the tumor to help guide treatment. Testing includes DNA-based tests to identify changes in the genes themselves, and RNA-based tests to measure how those genes behave, giving your care team a fuller picture of your tumor makeup and available treatment options.

How Is KRAS Testing Done?

Testing is usually done at diagnosis or when treatment changes. Your doctor will need to test your tumor through a tissue or blood (liquid) biopsy. There are several different types of tests that doctors use to look for changes, or biomarkers in your cells:

  • Fluorescence in Situ Hybridization, or FISH, analysis is a common genetic test. FISH analysis looks at changes in the chromosomes through tissue under a microscope.
  • Immunohistochemistry (IHC) looks for proteins in the cell under a microscope.
  • Next-generation sequencing (NGS), also called comprehensive biomarker testing, is when tissue from a patient's tumor (gathered from a biopsy) is placed in a machine that looks for many possible biomarkers at one time.
  • Reverse transcription polymerase chain reaction (RT-PCR) is a laboratory method used to make many copies of a specific genetic sequence for analysis.

Your doctor may perform several of these tests at the same time to help confirm results. Different biomarkers rely more heavily on certain tests.

KRAS mutations are typically identified using NGS, which can detect many KRAS variants at once. Some may also use PCR for common mutations like KRAS G12C. Liquid biopsy may be used to monitor KRAS mutations over time. 

Learn more about the different types of biomarker tests. 

Understanding Your KRAS Test Results

Once testing is complete, your results will identify whether a KRAS mutation is present and help determine which treatment options may be appropriate.

A KRAS mutation (especially G12C) may make the patient eligible for KRAS‑targeted therapies or mutation‑specific clinical trials.

If no KRAS mutation is found, other biomarkers (EGFR, ALK, ROS1, BRAF, PD‑L1, etc.) may guide treatment instead. 

If results are inconclusive, additional testing (often a liquid biopsy or repeat tissue test) may be needed to confirm whether a KRAS mutation is present. 

How KRAS Results Influence Treatment

A KRAS-positive test result can help guide treatment decisions.

Currently, the standard first-line therapy for a patient with KRAS-positive lung cancer depends on the stage of their cancer. Treatment may include surgery, radiation therapy, chemotherapy, immunotherapy, or a combination of these approaches.

For patients with a KRAS G12C mutation, there are currently two approved targeted therapy pills, also called KRAS inhibitors. These therapies are currently used as a second-line therapy.

  • Sotorasib (Lumakras)
  • Adagrasib (Krazati)

If a patient's cancer stops responding to chemotherapy, immunotherapy, or a combination of both, sotorasib (Lumakras) or adagrasib (Krazati) may be recommended.

Learn more about treating KRAS G12C mutations from Dr. Sandip Patel (video).

Many other medicines are being studied in clinical trials to treat KRAS-positive lung cancer. All patients with lung cancer should discuss clinical trials with their doctor.

Watch as Dr. Melissa Johnson discusses clinical trials and KRAS-positive lung cancer (video).

Questions to Ask Your Doctor

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

  • What is the goal of this treatment?
  • What are the potential side effects?
  • 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.

What to Do After a KRAS Diagnosis

Someone with a KRAS‑positive lung cancer diagnosis can take several empowering steps to stay ahead of their care. These are general medical information steps, not personal medical directives, and it’s important to work closely with a qualified healthcare professional for decisions about diagnosis or treatment. 

KRAS mutations come in several forms (such as G12C, G12D, G12V), and knowing the exact subtype helps determine whether targeted therapies or clinical trials may apply.

Instead of single‑gene testing, next‑generation sequencing (NGS) can identify KRAS and other important biomarkers (like STK11, KEAP1, TP53, PD‑L1) that may influence treatment planning.

If tissue was limited or if additional information is needed later, a blood‑based ctDNA test can sometimes detect KRAS mutations or emerging resistance patterns.

KRAS testing is standard in non‑small cell lung cancer because it can directly affect treatment options, including eligibility for KRAS‑targeted therapies.

Having your reports on hand helps you track what has already been tested, understand your mutation profile, and avoid delays if you seek a second opinion or explore clinical trials.

Support and Patient Experiences

Whether you're newly diagnosed or navigating treatment, support resources and patient experiences can help you better understand your options and connect with others.

Connect with Support Resources

Hear from Other Patients

In the videos below, patients share their advice for people newly diagnosed with KRAS-positive lung cancer, including the importance of hope, self-advocacy, support, and exploring available treatment options.

KRAS-positive lung cancer patient, Jennifer, shares what she would tell a newly diagnosed KRAS-lung cancer patient.
Lung cancer survivor, Nancy, shared her advice for KRAS+ lung cancer patients.

Video transcripts

Lung cancer research can move at a rapid pace. Always speak with your doctor about the most up-to-date treatment guidelines.

Medically reviewed by: Jorge Gomez, MD
Last reviewed: June 2026 

Page last updated: August 13, 2026

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