What are other Names for this Test? (Equivalent Terms)
- KRAS Exon 4 Mutation Analysis
- KRAS Exon 4 Mutation Test
What is KRAS Mutation Analysis Test? (Background Information)
- KRAS (pronounced “kay-raz”) exon 4 mutation is an alteration in the gene that gives instructions for the KRAS protein. The KRAS mutation is associated with cancers, including colorectal and lung cancers
- The KRAS protein plays a role in increasing the rate of growth and division of cells. Abnormalities in the KRAS gene may cause defects in the KRAS protein that make it more active than normal
- An overactive KRAS protein causes excessive stimulation of cellular pathways for growth and division, leading to uncontrolled cell proliferation, and thus cancer
- As part of the normal conversion of genetic information into protein, cells create intermediate compounds that are often further modified (a process called alternative splicing)
- Alternative splicing involves the removal of segments of genetic material and joining remaining segments together. Segments that are removed are called introns, while those that remain are called exons
- The KRAS Exon 4 Mutation Analysis Test is a genetic test that detects abnormalities in the KRAS gene in exon number 4. It is used to guide treatment for cancer by assisting in the selection of appropriate therapeutic drugs, such as tyrosine kinase inhibitors (TKIs), and disqualifying certain drugs from being used
The molecular testing, in general, can be performed using a variety of methods. Some of these methods include:
- In situ hybridization technique, such as fluorescence in situ hybridization (FISH)
- Immunohistochemistry (IHC)
- Next-generation sequencing (NGS)
- Polymerase chain reaction (PCR)
- Comparative genomic hybridization (CGH)
- Karyotyping including spectral karyotyping
- mRNA analysis
- Tissue microarrays (TMAs)
- Southern blot test
- Northern blot test
- Western blot test
- Eastern blot test
The methodology used for the test may vary from one laboratory to another.
Note: Molecular testing has limitations due to the molecular method and genetic mutational abnormalities being tested. This can affect the results on a case-by-case basis. Consultation with your healthcare provider will help in determining the right test and right molecular method, based on individual circumstances.
What are the Clinical Indications for performing the KRAS Exon 4 Mutation Analysis Test?
Following are the clinical indications for performing the KRAS Exon 4 Mutation Analysis Test:
- Monitoring cancer therapy
- Gauging potential efficacy of TKIs
- Assessing treatment options for colorectal, lung, and other cancers
In general, the molecular genetic testing is undertaken in the following situations:
- To assist (and in some cases, confirm) the initial diagnosis
- To distinguish other tumors/conditions that have similar histological features, when examined by a pathologist under the microscope
- To help in determining treatment options
- To confirm recurrence of the tumor: Tumor recurrence can either be at the original tumor site, or at a distant location (away from the initial site)
How is the Specimen Collected for KRAS Exon 4 Mutation Analysis Test?
Following is the specimen collection process for KRAS Exon 4 Mutation Analysis Test
The specimen sample requirements may vary from lab to lab. Hence, it is important to contact the testing lab for exact specimen requirements, before initiating the testing process.
- Sample on which the test is performed may include:
- Fresh tumor tissue during biopsy
- Formalin-fixed paraffin-embedded solid tumor tissue (FFPE tumor tissue), often referred to as paraffin block of the tumor
- Unstained tissue slides
- Process of obtaining the sample: As outlined by the laboratory testing facility
- Preparation required: As outlined by the laboratory testing facility
- In some cases, a different source of specimen (such as peripheral blood, bone marrow biopsy specimen, or other body fluids) may be acceptable to the laboratory performing the test
- Occasionally, additional samples may be required to either repeat the test or to perform follow-up testing
- Depending on the location of testing, it may take up to 2 weeks’ turnaround time, to obtain the test results
- Many hospitals preserve the paraffin blocks for at least 7 years. In general, older paraffin blocks (over 5 years) may affect the detection of specific mutations, due to degradation of the tumor specimen over time
Cost of KRAS Exon 4 Mutation Analysis Test:
- The cost of the test procedure depends on a variety of factors, such as the type of your health insurance, annual deductibles, co-pay requirements, out-of-network and in-network of your healthcare providers and healthcare facilities
- In many cases, an estimate may be provided before the test is conducted. The final amount may depend upon the findings during the test procedure and post-operative care that is necessary (if any)
What is the Significance of the KRAS Exon 4 Mutation Analysis Test Result?
- A positive value for the KRAS Exon 4 Mutation Analysis Test may disqualify certain therapeutic drugs namely, EGFR-specific TKIs, from being used to treat lung, colorectal, and other cancers
The laboratory test results are NOT to be interpreted as results of a "stand-alone" test. The test results have to be interpreted after correlating with suitable clinical findings and additional supplemental tests/information. Your healthcare providers will explain the meaning of your tests results, based on the overall clinical scenario.
Additional and Relevant Useful Information:
- The KRAS protein acts sequentially after, and independent of, another cancer-causing mutation of a gene called EGFR. EGFR gives instructions for the EGFR protein (epidermal growth factor receptor protein), which when altered is a significant cause of many cancers
- The most commonly used TKI is imatinib. Others include lapatinib, nilotinib, and sorafenib
- Imatinib gained FDA approval in 2001. Previously, only highly toxic drugs, such as busulfan and hydroxyurea, were used
- Many laboratories may not have the capability to perform this test. Only highly-specialized labs with advanced facilities and testing procedures may perform this test
Certain medications that you may be currently taking may influence the outcome of the test. Hence, it is important to inform your healthcare provider, the complete list of medications (including any herbal supplements) you are currently taking. This will help the healthcare provider interpret your test results more accurately and avoid unnecessary chances of a misdiagnosis.
What are some Useful Resources for Additional Information?
The following DoveMed website link is a useful resource for additional information:
Please visit our Laboratory Procedures Center for more physician-approved health information:
References and Information Sources used for the Article:
https://ghr.nlm.nih.gov/primer/testing/genetictesting (accessed on 05/10/2017)
https://www.cdc.gov/mmwr/preview/mmwrhtml/rr5806a1.htm (accessed on 05/10/2017)
http://www.nature.com/gim/journal/v10/n5/full/gim200852a.html (accessed on 05/10/2017)
http://pediatrics.aappublications.org/content/106/6/1494 (accessed on 05/10/2017)
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