KRAS and BRAF Testing for Colorectal Cancer (CRC)
Overview and Clinical Significance:
RAS genes are the most common targets for somatic gain-of-function mutations in
human cancers. Activating RAS mutations occur in 30% of human cancers and specific
RAS genes are mutated in different cancers, including colorectal cancer (CRC), non-small
cell lung cancer, pancreatic cancer and others.
Some mutations in the KRAS gene (about 40% of colorectal cancer patients) are associated
with poor prognosis and lack of response to anti-epidermal growth factor receptor
(anti-EGFR) therapy. In July 2009, the Food and Drug Administration (FDA) approved
labeling changes to two EGFR antagonists, cetuximab and panitumumab, stating that
these agents are not recommended for the treatment of colorectal cancer (CRC) harboring
KRAS mutations. Thus, determination of KRAS mutation status in these tumors is critical
when evaluating a patient for anti-EGFR therapy.
The American Society of Clinical Oncology (ASCO) has further recommended that all
patients with metastatic colorectal cancer for whom EGFR antagonists are being considered
should be specifically tested for KRAS mutational status at codons 12 and 13.
BRAF is a downstream molecule from KRAS in a signaling pathway involved in cell
cycling, and, like KRAS, mutations in BRAF are observed in CRC. BRAF mutations,
such as V600E, are responsible for an additional 12-15% of patients who fail to
respond to anti-EGFR treatment.
Data from the CRYSTAL trial suggest that BRAF mutations are also indicative of poor
prognosis and the National Comprehensive Cancer Network (NCCN)
Colon Cancer Guideline Update 2010 states that testing for mutations in BRAF should
occur when KRAS testing indicates KRAS wild type.
Asuragen Tests
Asuragen KRAS and BRAF Laboratory developed tests (LDTs), validated
in the CLIA lab, are intended to be used and interpreted in conjunction with all
other available clinical and laboratory information when evaluating anti-EGFR treatment
options for colorectal cancer patients. The test is validated for
use with CRC formalin-fixed paraffin-embedded (FFPE) tissue specimens that contain
at least 40% tumor area, or that can be enriched to that tumor content in the course
of a histological specimen review. The test has not been validated on other specimen
types or other human malignancies.
Asuragen KRAS and BRAF LDTs are available in several configurations
(see Figure 1) and were optimized for maximum coverage and sensitivity. The KRAS
7 Mutation Test allows for detection of the seven clinically relevant KRAS mutations
in codons 12 and 13. The KRAS 12 Mutation test configuration enables detection of
an additional five rare KRAS mutations in codon 13. By testing these 5 additional
codon 13 mutations the increase in coverage is greater than if
the test included codons 59, 61 and 146 combined (about 10 additional
mutations) [calculations based on data analysis from COSMIC database accessed May
28, 2010].
Figure 1: Available Test Configurations
Tests Process
How to order the new KRAS and BRAF tests from Asuragen
CLIA Patient Testing: Test Requisition Form can be downloaded
here
CLIA Research Testing: Sample Submission Form can be downloaded
here
Click here to download Specimen Shipping and Handling Instructions
Contact our CLIA Laboratory at 512-681-5200 or 1-877-777-1874 for any additional
information.
Specimen requirements
FFPE tissue or cell block
- A minimum one 10 µm unstained FFPE slide with a tissue surface
area equal or greater than 1cm2, containing ≥40% abnormal area content
and one H&E stained slide for pathology assessment.
- FFPE clinical blocks containing ≥40% abnormal area (additional
charges will apply for generation of H&E slide and pathology review).
- For specimens with <40% abnormal area content, Asuragen’s pathologist
will determine if the specimen abnormal area content can be enriched to the required
40%.
Billing
Asuragen bills third parties (private insurance or Medicare), patient, or hospital.
Note: Asuragen does not accept Medicaid. Asuragen cannot accept
samples from New York or California until Asuragen has received state licensure
in those states.
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