The KRAS Test Procedure
KRAS is a new biomarker being used to select the best treatment for individual colorectal cancer (CRC) patients. The KRAS gene in a CRC tumor may be 'wild-type' or 'mutant' and this KRAS 'status' will help determine which treatment the patient is given.1 This step-by-step guide outlines the laboratory testing procedure used to determine KRAS status:
STEP 1:
Before the KRAS test begins, a quality control check takes place in which the sample is evaluated by a pathologist to confirm that cancer cells are present
STEP 2:
The tissue sample is then removed from the slide in order for the KRAS 'status' test to be performed
STEP 3:
The tumor DNA from the tissue sample is purified
STEP 4:
The tumor DNA is checked for purity as part of quality control procedures
STEP 5:
A highly sensitive KRAS specific test, based on a polymerase chain reaction (PCR), uses labeled probes to amplify DNA in order to detect the presence of mutated KRAS
STEP 6:
The products of the amplification are measured to determine whether the tumor has the wild-type KRAS gene or the mutant version. This enables a more targeted selection of treatments to be made for each patient, according to the KRAS status of their tumor
KRAS testing can be done via polymerase chain reaction (PCR) as outlined above. In addition, other options are now available.
The NCCN guidelines state2:
- No specific methodology is recommended (sequencing, hybridization, PCR, etc.)
- The testing can be performed on the primary colorectal cancers and/or the metastasis as literature has shown that the KRAS mutations are similar in both specimen types
Validated kits can be obtained e.g. from Qiagen (www.qiagen.com)
