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Colorectal cancer focused gene panel

Also known as: Colorectal panel, KRAS, NRAS, BRAF, PIK3CA

Test category:

Oncology - Colorectal cancer

Use of test

Purpose:

The presence of specific activating mutations in the KRAS and NRAS genes in metastatic colorectal cancer indicates a reduced likelihood of treatment response to anti-EGFR therapy. Mutations in the BRAF and PIK3CA genes may also have implications for targeted therapy.

Utility:

The presence of specific KRAS or NRAS mutations is associated with reduced likelihood of response to anti-EGFR antibody targeted therapy. In colorectal cancer, presence of a BRAF mutation may be associated with reduced likelihood of response to targeted  therapy with anti-EGFR antibodies, and is associated with prognosis.

A normal test result (no RAS mutations) indicates that the patient's tumour is more likely to respond to anti-RAS therapies. An abnormal test result (specific mutations identified) indicates that the tumour is likely to be resistant to anti-RAS therapies.

In mismatch-repair deficient colorectal cancers, the absence of a BRAF mutation is associated with an increased probability of the patient having Lynch syndrome, an inherited DNA mismatch-repair deficiency.

PIK3CA mutations may also be associated with prognosis and reduced likelihood of response to anti-EGFR antibody therapy.

This test can be expanded to a full Find It panel that simultaneously evaluates the mutation status of tumour DNA at more than 140 well-characterised positions (hotspots) and more than 20 exons in no less than 30 cancer-associated genes.

Ethical considerations:

This is an assay for non-heritable mutations. It does not raise issues of ethics or consent that are different from most other investigations ordered in the routine care of a patient.

Methodology:

Targeted analysis of clinically relevant activating mutations in BRAF codon 600, KRAS and NRAS codons 12, 13, 59, 61, 117, 146 and PIK3CA exons 10 and 21. This assay detects targeted single nucleotide variants and insertion/deletion mutations (of up to 24 base pairs in size). Fusion genes and copy number variants will not be detected. Very low level targeted variants (<5% variant allele frequency) may not be detected.

For further details, please refer to the description of the full Find It panel.

Requesting the test

Ordering:

This test is usually requested by a surgeon or oncologist. Please use the specific request form (see link below).

Request Form:

Download the solid tumour somatic mutation request form.

Sample required:

Formalin-fixed, paraffin embedded tissue (FFPE) - 15 sections of 4 uM thickness, dried overnight at 37°C onto charged/coated slides.

Special instructions:

Please stain the first section with H&E, and label each slide with patient and block identifiers. Label the unstained sections sequentially (slides 2-15). The request should be accompanied by the somatic mutation request form (above) and a copy of the original histopathology report.

Turnaround time:

7 business days from receipt of sections by the testing laboratory.

Price:

This test has a Medicare rebate which, subject to the requirements of the Medicare descriptor being met, may cover all or part of the cost.

Rebate:

The Medicare details, including descriptor and schedule fee, are listed under MBS item 73338.

Click here for our billing policy.