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KRAS Codon 146 Mutational Analysis

KRAS Codon 146 Mutational Analysis

Indication:  

The KRAS gene is mutated in over 30% of colorectal cancers. The majority (~82%) of reported mutations are in codon 12. Mutations at codons 13 and 61 contribute to a lesser degree, accounting for ~17% and ~1% respectively. Recently, activating mutations involving codon 146 of exon 4 of KRAS have been described with frequencies ranging from 1-4% in colorectal cancers. Rare cases of codon 146 mutations were also found in acute myeloid leukemia and in acute lymphoblastic leukemia cell lines.  Mutations in codons 61/146 of KRAS have been shown to predict resistance to EGFR-targeted therapy (cetuximab), especially in patients that are wild-type at codons 12 and 13 in one study. Some studies also report that the frequency of codon 146 mutations is higher than the frequency of mutations in codon 61. The assay detects activating mutations in codon 146 of KRAS.

Methodology:  

This test is performed by PCR-based Sanger sequencing of DNA to examine the mutation status of codon 146 in exon 4 of KRAS.

Test Parameters:  

This assay will detect mutations present in exon 4 of KRAS. The sensitivity of the Sanger sequencing assay is 20% of variant sequence in the background of wild-type sequence.

Turnaround Time:

7-10 days

Sample Requirements:

• 10 ug of purified DNA, sent on dry ice

or

• Four to six unstained recut slides of formalin-fixed, paraffin embedded tissue containing adequate amounts of tumor to be analyzed (See Sensitivity.)
The area of tumor to be analyzed should be indicated by circling the area on the bottom side of the slide or in a separate H&E-stained guide section.
Please provide a copy of the corresponding pathology report.

CPT Codes:

81479

Additional charges may apply for tissue extraction.

The CPT codes provided are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payer being billed.


© 2014 The University of Texas MD Anderson Cancer Center