KRAS, NRAS and BRAF Mutation Testing in Colorectal Tumour Samples

Introduction

KRAS, NRAS and BRAF are oncogenes frequently somatically mutated in colorectal tumours. Somatic KRAS, NRAS and BRAF mutations result in a specific gain of function and almost exclusively affect codons 12, 13 and 61 of the KRAS and NRAS genes and codon 600 of BRAF. As KRAS, NRAS and BRAF lie downstream of EGFR in the EGFR signalling pathway, presence of an activating KRAS, NRAS or BRAF mutation in a colorectal tumour predicts a likely poor response to EGFR inhibiting therapy. Frequency of KRAS, NRAS, BRAF mutations in colorectal cancer (CRC) samples is approximately 36–40%, 1-6% and 8–15% respectively.

Referral information

Colorectal cancer samples from recently diagnosed patients.  Referrals are from Oncologists and samples are received via pathologists. Samples should have undergone pathology review to ensure that the sample submitted for analysis is of appropriate pathology and the tumour cell content is sufficient to permit mutation detection. Formalin fixed paraffin embedded (FFPE) tissue is accepted, however the tissue must be sent as a minimum of 5 x 5µM thick sections sealed in a clean 1.5mL Eppendorf tube. A minimum of 20% tumour tissue in the submitted sample is required for optimum mutation detection (see sample requirements).

Price & reporting times

The current charge of all three codons of KRAS and NRAS is £100 for each gene on Christie SLA and £100 if invoiced separately.

Test Price (NHS & non-NHS) TRT*
BRAF codon 600 (p.V600E) POA 7 cd
KRAS codons 12, 13 and 61 POA 7 cd
NRAS codons 12, 13 and 61 POA 7 cd

Test validation & quality assurance - information for users

The pyrosequencing assays have been validated in house using a series of CRC and pancreatic samples.  Each sample is assayed in triplicate to ensure consistency.

Sample requirements

5 x 5µM FFPE unstained slide mounted sections (without coverslips) from a tissue block selected to have maximum neoplastic cell content. If neoplastic cell content is less than 20% and the sample is suitable for macrodissection, please send an accompanying H&E stained guide slide prepared from a neighbouring section with the region of neoplasia clearly marked out. Where neoplastic cell content is greater than 30%, 5 x 5 µM FFPE sections as unmounted scrolls in a clean, unused, tube or container manufactured under aseptic conditions is acceptable.

Referral guidelines

Please see our referral guidelines for more information.

OMIM Number(s) - 190070, 164790, 164757

Gene(s) - KRAS, NRAS, BRAF

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