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KRAS Codon 146 Mutational Analysis


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.


PCR-based DNA Sanger sequencing. This assay is also available on next generation sequencing platforms.

Test Parameters

This assay will detect mutations in codon 146 in exon 4 of the KRAS gene. The sensitivity of detection is approximately one mutated cell per five total cells in the sample (20%).

Turnaround Time

10 days

Sample Requirements

Formalin-fixed, paraffin embedded tissue blocks or 10 unstained slides containing adequate amounts of tumor to be analyzed (see above sensitivity), with areas to be tested clearly indicated on the slides/block. Comparison of normal and tumor, or several different areas of tumor can be done, for additional charge.

Please provide a copy of the corresponding pathology report.

CPT Codes


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