KRAS Mutation

April 29, 2026

This page was reviewed under our medical and editorial policy by Matthew Lee, M.D., M.P.H., Medical Oncologist and Assistant Professor of Medical Oncology, City of Hope^® Cancer Center Duarte.

KRAS is a gene that tells cells when to grow, mature and die. It stands for Kirsten rat sarcoma, and has many other names as well. The normal, unchanged form of the gene is known as wild-type KRAS, but if KRAS mutates, it has the ability to lead to cancer formation. Genes with this possibility are called oncogenes.

KRAS gene mutations are linked to certain types of cancer, such as colorectal cancer, pancreatic cancer and non-small cell lung cancer.

What Is a KRAS Mutation?

The KRAS gene guides the production of a cell protein known as K-Ras. This protein sends signals from the outside to the inside of cells. These signals tell cells to grow and divide or to perform different functions. In this way, the K-Ras protein acts like a switch, turning cell functions off and on.

When KRAS gene mutations are present in a cell, the K-Ras protein over-signals and stays in the “on” position too long, telling the cell to grow uncontrollably. This creates a tumor.

The KRAS gene is a type of Ras oncogene, which, when changed, may make healthy cells turn cancerous. Other genes in the Ras oncogene family include HRAS and NRAS. For all of these oncogenes, changes may affect how cells grow, divide and die.

If a person is diagnosed with certain types of cancer, doctors may recommend testing of blood or tumor tissue samples for a KRAS mutation. Cancers with a KRAS mutation may respond better to certain treatments and not as well to others. Knowing if a person has a variant in the gene may help guide cancer treatment decisions.

In some cases, the word “variant” may be used instead of “mutation.” Both refer to a change that has occurred in the sequence of a person’s DNA, the molecule that houses the instructions for making proteins in the body. These DNA changes cause permanent changes in the way the gene operates. Sometimes a change in a gene leads to disease, and sometimes it does not. Some experts prefer the term variant, since it seems to cover the wider range of nonharmful (benign) as well as harmful changes in genes.

KRAS mutations, or variants, are not inherited from parents, but happen during one’s life. When gene changes are in the parents’ egg and sperm cells (germline variant), the variant is passed on (inherited). Gene variants that happen in other types of cells after birth during the course of one’s life (known as somatic mutations) may affect that person but are not passed on to the next generation. These noninherited mutations, like KRAS, may be caused by factors in the environment (for example, exposure to radiation from the sun or smoking).

About 11.6% of all carcinomas include a KRAS mutation, but that number varies by cancer type.

KRAS Mutation and Lung Cancer

Multiple types of KRAS mutations may lead to lung cancer, and about 15% to 25% of people with lung cancer have some type of KRAS mutation, according to the U.S. National Library of Medicine. About half of people with lung cancer have the G12C mutation, according to the American Lung Association.

Knowing which KRAS variant is present helps guide lung cancer treatment choices, which may include surgery, radiation therapy, chemotherapy, lung cancer immunotherapy or a combination of these treatments.

If a patient’s cancer has specifically KRAS G12C mutation, a targeted treatment, such as Lumakras^® (sotorasib) or Krazati^® (adagrasib), may be recommended after progressing on immunotherapy and chemotherapy. These drugs are oral tablets taken once or twice daily. 

Side effects of Lumakras and Krazati may include:

• Nausea
• Vomiting
• Diarrhea
• Fatigue
• Muscle pain
• Swelling in the legs and feet
• Shortness of breath
• Decreased appetite

More serious side effects may include decreased red and white blood cell counts, liver and kidney problems, lung and heart problems, and electrolyte imbalances.

KRAS Mutation and Pancreatic Cancer

About 11.6% of pancreatic cancers involve KRAS mutations, but that varies by subtype. For instance, 81.72% of pancreatic adenocarcinomas have the KRAS mutation.

Some types of pancreatic cancer have the KRAS G12C gene mutation. If the cancer is found to have the KRAS G12C gene change, doctors may recommend Lumakras (sotorasib) or Krazati (adagrasib). These drugs are oral tablets taken once or twice daily, and they may be used when other treatments have not worked or when cancer has gotten worse despite other treatments.

KRAS Mutation and Colorectal Cancer

About 38% of colorectal cancers include KRAS mutations, and a biopsy may be performed to check for the KRAS G12C mutation.

The drugs Lumakras (sotorasib) or Krazati (adagrasib) may be treatment options. Krazati may be prescribed along with Erbitux^® (cetuximab) for advanced colorectal cancer that continues to grow after other treatments have been given. While Lumakras is currently approved only to treat non-small cell lung cancer with the KRAS G12C mutation, sometimes doctors prescribe it off-label to treat colorectal cancer.

KRAS Mutation and Other Cancers

Research is ongoing to identify other cancers that are linked to a KRAS mutation as well as ways to use existing treatments in new ways to treat cancers with a KRAS mutation.

Some bile duct cancers and gallbladder cancers have the KRAS G12C mutation and may be treated with Krazati after other treatments have been tried.

KRAS mutations have also been found in blood cancers such as acute myeloid leukemia. As new research findings become available, this may be another type of cancer treated with these drugs.

Researchers are currently working on additional inhibitor medications that work across other KRAS mutations, not just the G12C variant, since other variants in the KRAS gene may lead to cancer development.

KRAS Testing

Doctors may recommend testing for KRAS mutations anytime they suspect it may be present. Types of cancer that may have a KRAS mutation include:

• Colorectal cancer
• Pancreatic cancer
• Non-small cell lung cancer
• Bile duct cancer
• Gallbladder cancer

Tests for KRAS mutations include the following.

Polymerase chain reaction (PCR): This laboratory test makes copies of a piece of DNA to check for chromosome or gene changes that are present in cancer.

Sequencing technologies: These tests include Sanger sequencing and next-generation sequencing (NGS). Computers are used to analyze DNA from tissue samples to find mutations in specific genes. The results show specific parts of DNA and how it functions.

KRAS Mutation Test Results

PCR and sequencing tests for KRAS mutations typically take about three hours to complete. After the tests are completed at a laboratory, the results are shared with the doctor who ordered them. At City of Hope^®, doctors use the positive or negative results from these tests to help guide treatment for patients and evaluate for potential clinical trials.