KRAS Gene Mutation Analysis, Colorectal Cancer (CRC)

CPT: 81275; 88381
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Test Details

Use

This KRAS assay is a real-time qualitative PCR test performed on the Rotor-Gene Q MDx instrument for the detection of the seven most common somatic mutations in the human KRAS oncogene, using DNA extracted from formalin-fixed paraffin-embedded (FFPE), colorectal cancer (CRC) tissue. This assay is intended to aid in the identification of CRC patients for treatment with cetuximab (Erbitux®), based on a KRAS "no mutation detected" test result. The presence of these mutations correlates with a lack of response for certain EGFR inhibitor cancer therapies in patients with metastatic colorectal cancer.

Limitations

The KRAS test is designed to detect seven mutations in codons 12 and 13 of the KRAS gene. These seven mutations account for >97% of all reported KRAS mutations in CRC patients. Samples with results reported as "no mutation detected" may harbor KRAS mutations that are not detected by the assay.

Detection of mutation is dependent on sample integrity and the amount of amplifiable DNA present in the specimen. The methods used in this assay are highly selective and, depending on the total amount of DNA present, can detect approximately 1% to 5% of mutant DNA in a background of wild-type genomic DNA.

Methodology

Amplification refractory mutation system (ARMS) and real-time polymerase chain reaction (PCR) using Scorpions™ technology

Specimen Requirements

Specimen

Formalin-fixed, paraffin-embedded (FFPE) tissue block or slides from colorectal cancer

Volume

Four unstained slides and one matching H&E-stained slide at 5 μM or formalin-fixed, paraffin-embedded tissue block

Minimum Volume

Two unstained slides and one matching H&E-stained slide at 5 μM. Samples with >4 mm² and ≥20% tumor content are preferred.

Container

Slides, blocks

Storage Instructions

Maintain specimen at room temperature.

Causes for Rejection

Tumor block containing no tumor tissue; tumor fixed in a heavy metal fixative; broken or stained slides

Clinical Information

Special Instructions

Please provide a copy of the pathology report. Direct any questions regarding this test to customer service at 800-345-4363.

References

Bokemeyer C, Van Cutsem E, Rougier P, et al. Addition of cetuximab to chemotherapy as first-line treatment for KRAS wild-type metastatic colorectal cancer: pooled analysis of the CRYSTAL and OPUS randomized clinical trials. Eur J Cancer. 2012 Jul; 48(10):1466-1475.
Di Fiore F, Blanchard F, Charbonnier F, et al. Clinical relevance of KRAS mutation detection in metastatic colorectal cancer treated by cetuximab plus chemotherapy. Br J Cancer. 2007 Apr 23; 96(8):1166-1169.
Qiagen Therascreen KRAS RGQ PCR Kit Instructions for Use (Handbook), 07/2012.
Schuch G, Kobold S, Bokemeyer C. Evolving role of cetuximab in the treatment of colorectal cancer. Cancer Manag Res. 2009 Jul 23; 1:79-88
Tejpar S, Celik I, Schlichting M, et al. Association of KRAS G13D tumor mutations with outcome in patients with a metastatic colorectal cancer treated with first-line chemotherapy with or without cetuximab. J Clin Oncol. 2012 Oct 10; 30(29):3570-3577.

LOINC® Map

Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
480875 KRAS Mutation Analysis, CRC 480876 K-ras Mutation Analysis Result 21702-6
480875 KRAS Mutation Analysis, CRC 480877 Block Number: N/A
480875 KRAS Mutation Analysis, CRC 480903 Microdissection Performed 8100-0
480875 KRAS Mutation Analysis, CRC 480907 Nucleotide Change: 48004-6
480875 KRAS Mutation Analysis, CRC 480937 Amino Acid Change: 48005-3
480875 KRAS Mutation Analysis, CRC 480908 Background: 21703-4
480875 KRAS Mutation Analysis, CRC 480938 Director Review: 72486-4
480875 KRAS Mutation Analysis, CRC 511973 Putaway N/A

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