NRAS Mutations

Please note that NRAS Mutations is intended for solid tumors. For testing related to hematologic malignancies, please order Heme Single Gene by NGS [HCAPSG]. Consultation with a Director can be requested to determine the appropriate testing. Please contact the laboratory at 206-598-6429 for further questions.

This test detects mutations in the NRAS gene, which includes codons 12, 13, 61, 117, and 146. In colorectal cancer, acquired NRAS mutations at these codons are associated with resistance to drugs that target the epidermal growth factor receptor (including cetuximab and panitumumab). This test can normally detect a heterozygous mutation if it is present in more than about 5% of the cells in the sample.

NRAS (also known as Neuroblastoma-RAS) is a commonly mutated oncogene in human cancer. The majority (97%) of mutations involve codons 12, 13, and 61. NRAS mutational status is useful in guiding therapy in patients with certain cancers including colon cancer and melanoma.

• Colon cancer with wild type NRAS and KRAS, may respond to antibody therapy targeted at the EGF receptor (De Mattos-Arruda 2011, De Roock 2010), while NRAS mutated colon cancer is much less likely to respond anti EGFR antibody therapy (De Mattos-Arruda 2011, De Roock 2010, Peeters 2010, Schrirripa 2015). NRAS mutations occur in ~2-6% in colorectal cancers (COSMIC; Irahara et al. 2010; Janku et al. 2011).
• Melanoma with mutant NRAS is usually mutually exclusive of BRAF and KIT mutations. Ongoing studies are evaluating MEK inhibitors, which is downstream of NRAS, in patients with NRAS mutated metastatic melanoma (Johnson 2014, Zhao 2014). NRAS mutations are found in approximately 15 to 20% of melanomas.

Requirements for Specimen Selection

• To ensure clinically relevant results, the most recent and/or metastatic sample is preferred to older specimens, provided sufficient tumor is present (see point 2).
• To ensure detection of all types of mutations there should be at least 10% tumor cells in the tissue area processed for DNA for mutation detection and 20% tumor cells for microsatellite instability evaluation. If there is more than one tissue block, please provide the block that has the greatest percentage of neoplastic nuclei.
• Tissue samples and pathology reports will be reviewed by directors upon receipt for acceptability prior to testing. Director consultation for tissue selection is available if needed (contact Genetics lab).

Specimen Types

Tissue samples

Send one of the following:

1. Slides: 1 slide at 4-micron thickness stained with hematoxylin-and-eosin (H&E) AND 10 unstained, non-baked slides at 10-micron thickness (a minimum of 5 unstained slides is acceptable). Unstained slides can be on charged or uncharged slides.
2. Tissue Blocks: Provide complete formalin-fixed tissue block containing tumor tissue. Tissue block will be returned at completion of testing.
3. Fresh/frozen tissue: 5 microgram tissue in cell culture medium or frozen tissue stored at -20C. Tumor percentage will not be determined prior to sequencing studies.

NOTE: In order to ensure that enough DNA is obtained, the minimum acceptable tissue area is 10 square millimeters when ten 10-micron slides are supplied (1 cubic millimeter of tissue).

Purified DNA

5 micrograms ANDa reference hematoxylin-and-eosin (H&E) stained slide and pathology report required.

Bone Marrow

1 to 2 mL Bone Marrow in LAVENDER TOP (EDTA) tube

Blood

6 mL blood in LAVENDER TOP (EDTA) tube.

Alternative specimens may be acceptable with approval (contact: 206-598-1149).

For ADD-ON after prior testing, contact Genetics lab.

Unacceptable samples

We cannot accept decalcified samples or tissue samples treated with fixatives other than formalin.

Quantity:

Requested:

• Tissue: 10 unstained slides (10-micron thickness) plus one H&E-stained slide.
• Extracted DNA: 5 microgram Bone Marrow: 2 mL
• Blood: 6 mL

Minimum:

• Tissue: 5 unstained slides (10-micron thickness) plus one H&E-stained slide.
• Extracted DNA: 100-250 nanograms Bone Marrow: 1 mL
• Blood: 3 mL

Genetics Requisition

Providers with access to the UW implementation of Epic (i.e., FHCC, HMC, SCCA, UWMC, UWNW) may order this test using the order "UW Genetics and Solid Tumor Test Request." See tip sheet for more information (internal link).

Outside Laboratories: Ship at room temperature. Refrigerate blood, bone marrow and purified DNA for AML patients only.

Attach a copy of the pathology report for the tumor sample being submitted.

Hold slides or tissue blocks at room temperature.

For AML patients only, Refrigerate blood, bone marrow and purified DNA.

Stability: Unstained slides or tissue blocks stable at room temperature for at least 2 years.