This is the fourth part of our series about the condition based on our patient booklet “Fast Facts for Patients: Non-small Cell Lung Cancer with KRAS Mutation”. This article shows how your doctor knows your cancer is KRAS-positive and gives more information on KRAS in non-small cell lung cancer (NSCLC).

How Your Doctor Knows Your Cancer Is KRAS-Positive

To find out if your cancer is KRAS-positive, your doctor took a sample of cancer cells for testing (a biopsy). You may have had this done when you were first diagnosed, through a bronchoscopy or a needle biopsy. Or the cells may have been tested when you had surgery to remove your primary cancer.


NSCLC diagnosis: bronchoscopy and needle biopsy

Mutations can change in cancers as they grow, so your doctor may have re-tested your cancer cells. You may have had a blood test to do this, as genetic material from the cancer can in some cases be detected in blood samples. Your doctor may call this a ‘liquid biopsy’. Or you may have had a sample of secondary cancer taken, for example through a liver biopsy or a lymph-node biopsy.


Liquid biopsy, liver biopsy and lymph-node biopsy

More about KRAS

KRAS and its importance in the development of cancers was discovered over 30 years ago. It was first found in human cancer cells in the early 1980s. Soon, scientists had identified KRAS mutations in a whole range of cancers and realized its importance. They now calculate that some type of KRAS mutation is found in more than 1 in 5 (20%) of all cancers. Around 1 in 4 (25%) NSCLCs have KRAS mutations.

KRAS is associated with some cancer types more than others. KRAS mutations are nearly always found in adenocarcinomas (cancers that develop from gland cells in the lung). They are also more common in:

  • people who are or were tobacco smokers
  • people who were exposed to asbestos in the past
  • some ethnic groups compared with others: for example, they are found in up to 1 in 2 (50%) lung cancers diagnosed in White populations compared with 1 in 6 (around 17%) diagnosed in populations with lung cancer from Asia.

KRAS Subtypes in NSCLC

We now know that there are different types of KRAS mutations. These are named after the point in the gene where the mutation occurs and the change that takes place. As you can see, the G12C mutation is much more common than the others. The mutation occurs at position 12 in the KRAS gene and the amino acid C (cysteine) is substituted for the G (glycine) amino acid. Amino acids link together to form proteins.

KRAS subtypes in non-small cell lung cancer (NSCLC)

Treatments are being developed by several pharmaceutical companies that specifically target this mutation. Other treatments are being developed that hopefully will work for several types of KRAS mutation. Ask your specialist what type of mutations they’ve found in your lung cancer cells. It’ll help you to understand which treatments may help.

Questions for Your Doctor on Lung Cancer Mutation(s)

  • Have any mutations been found in my lung cancer cells?
  • What are the implications of the mutation(s) for my lung cancer?
  • Is there any treatment that targets the lung cancer mutation(s) I have?


Information based on Fast Facts for Patients: Non-small Cell Lung Cancer with KRAS Mutation (Karger, 2023).

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