KRAS Mutation
When you have colon cancer that has spread (metastatic) or non-small cell lung cancer and your health practitioner is considering an anti-EGFR drug therapy
A sample of tumor tissue
None
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How is it used?
This test detects the presence of the most common KRAS gene mutations in the DNA of cells in tumor tissue in order to help guide cancer treatment. KRAS mutation analysis is ordered primarily to determine if a person with metastatic colon cancer or non-small cell lung cancer is likely to respond to standard therapy, an anti-EGFR drug therapy. Tumors with the KRAS mutation do not respond to anti-EGFR therapy.
If a person's tumor is negative for the most common KRAS mutation, tests for other less common mutations not detected by the current test may be used to help predict therapeutic responses.
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When is it ordered?
A KRAS mutation test is usually ordered when an individual has been diagnosed with metastatic colon cancer or non-small cell lung cancer and the health practitioner is considering an anti-EGFR drug therapy. It may be performed at any time prior to the initiation of treatment.
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What does the test result mean?
If cancer tissue contains a KRAS mutation, then the affected person will not benefit from anti-EGFR drug therapies. The presence of a KRAS mutation also indicates a likely poorer prognosis, although the presence of a specific mutation cannot predict the severity or aggressiveness of an individual person's cancer.
A negative result on the KRAS test indicates that an individual's cancer may respond to anti-EGFR therapy, but the lack of a KRAS mutation as determined by the KRAS test does not ensure this. A negative test could occur when the tumor tissue sample is insufficient and/or when the cancer is heterogeneous (some cells contain the mutation and others do not). Additionally, there may be KRAS mutations that are not detected by some tests because of their particular location on a DNA chain. Other factors may also lead to resistance to anti-EGFR drugs.
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Is there anything else I should know?
Guidelines from both the American Society of Clinical Oncology and the National Comprehensive Cancer Network have recommended KRAS mutation testing prior to anti-EGFR therapy.
Anti-EGFR drug therapies include:
- For colon cancer, anti-EGFR antibodies such as cetuximab and panitumumab
- For non-small cell lung cancer, anti-EGFR tyrosine kinase inhibitors (TKIs) such as gefitinib and erlotinib
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Should everyone with cancer have KRAS mutation testing?
Testing is not generally indicated unless a person has colon cancer or non-small cell lung cancer and a health practitioner is considering anti-EGFR drug therapy.
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Would this testing and drug therapy be useful for other types of cancer?
It is possible, since KRAS mutations are found in other cancers. This is a focus for medical researchers, but it may be some time before the clinical utility of the testing and therapy in other cancers is determined.
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Is it necessary to repeat a KRAS mutation test?
This is not usually necessary but might occur if the health practitioner thought that the first sample tested might have been insufficient. In some cases, a health care provider may order a KRAS test that detects a mutation in another part of the DNA chain or another more rare KRAS mutation. Sometimes metastatic tumors may be not be accessible or have limited tissue for testing. In these cases, a sample (if available) from an individual's primary cancer may be obtained for testing. Frequently, if the primary tumor has a KRAS mutation, so will the metastatic tumor.
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Can this test be performed by my local laboratory?
It may be available in some larger laboratories, but must often it will be sent to a reference laboratory.
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Can this test be performed on my blood instead?
No, it is not the genetics of the person that is being evaluated; it is the genetic makeup of the cancer.