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Mayo Clinic Laboratories

Test ID NTRK NTRK Gene Fusion Panel, Tumor

Ordering Guidance

Multiple oncology (cancer) gene panels are available. For more information see Hematology, Oncology, and Hereditary Test Selection Guide.

Necessary Information

Pathology report (final or preliminary) at minimum containing the following information must accompany specimen in order for testing to be performed:

1. Patient name

2. Block number-must be on all blocks, slides and paperwork (can be handwritten on the paperwork)

3. Tissue collection date

4. Source of the tissue

Specimen Required

This assay requires at least 10% tumor nuclei.

-Preferred amount of tumor area with sufficient percent tumor nuclei: tissue 144 mm(2)

-Minimum amount of tumor area: tissue 36 mm(2).

-These amounts are cumulative over up to 10 unstained slides and must have adequate percent tumor nuclei.

-Tissue fixation: 10% neutral buffered formalin, not decalcified

-For specimen preparation guidance, see Tissue Requirement for Solid Tumor Next-Generation Sequencing. In this document, the sizes are given as 4 mm x 4 mm x 10 slides as preferred: approximate/equivalent to 144 mm(2) and the minimum as 3 mm x 1 mm x 10 slides: approximate/equivalent to 36 mm(2).

Preferred:

Specimen Type: Tissue block

Collection Instructions: Submit a formalin-fixed, paraffin-embedded tissue block with acceptable amount of tumor tissue.

Acceptable:

Specimen Type: Tissue slide

Slides: 1 stained and 10 unstained

Collection Instructions: Submit 1 slide stained with hematoxylin and eosin and 10 unstained, nonbaked slides with 5-micron thick sections of the tumor tissue.

Note: The total amount of required tumor nuclei can be obtained by scraping up to 10 slides from the same block.

Useful For

Identifying solid tumors that may respond to targeted therapies by simultaneously assessing for fusions involving targeted regions of the NTRK1, NTRK2, and NTRK3 genes resulting in fusion transcripts.

This test is not useful for hematologic malignancies.

Genetics Test Information

This test uses next-generation sequencing to identify rearrangements (fusions) involving targeted regions of the NTRK1, NTRK2, and NTRK3 genes.

The assay was designed to detect the most common NTRK gene fusions and novel gene fusion partners in the targeted gene regions. For more information see NTRK RNA Targeted Gene Fusions.

Of note, this test is performed to evaluate rearrangements (fusions) within solid tumor samples. This test is not intended for use for hematological malignancies.

Highlights

This test evaluates formalin-fixed, paraffin-embedded tumor slides from patients with advanced solid tumors for rearrangements (fusions) involving targeted regions of the NTRK1, NTRK2, and NTRK3 genes to identify candidates for targeted therapy. Current data suggests that solid tumors with NTRK rearrangements may be sensitive to multikinase inhibitors.

Additional Tests

Test ID	Reporting Name	Available Separately	Always Performed
SLIRV	Slide Review in MG	No, (Bill Only)	Yes

Testing Algorithm

When this test is ordered, slide review will always be performed at an additional charge.

Method Name

Polymerase Chain Reaction (PCR)-based Next-Generation Sequencing (NGS)

Reporting Name

NTRK Gene Fusion Panel

Specimen Type

Varies

Specimen Minimum Volume

See Specimen Required

Specimen Stability Information

Specimen Type	Temperature	Time
Varies	Ambient (preferred)
	Frozen
	Refrigerated

Reject Due To

Specimens that have been decalcified (all methods)
Specimens that have not been formalin-fixed, paraffin-embedded
Bone marrow in EDTA

Reject

Clinical Information

Targeted cancer therapies are defined as antibody or small molecule drugs that block the growth and spread of cancer by interfering with specific cell molecules involved in tumor growth and progression. Multiple targeted therapies have been approved by the US Food and Drug Administration for treatment of specific cancers. Molecular genetic profiling is often needed to identify targets amenable to targeted therapies and to minimize treatment costs and therapy-associated risks.

Fusions involving the NTRK1, NTRK2, and NTRK3 genes (ie, NTRK gene fusions) are oncogenic drivers of multiple types of pediatric and adult solid tumors. In solid tumors, the presence of an NTRK gene fusion is a biomarker for response to tropomyosin receptor kinase (TRK) inhibitor therapies.

This test assesses for fusions involving targeted regions of NTRK1, NTRK2, and NTRK3 genes. The results of this test can be useful in guiding treatment of individuals with advanced solid tumors.

See Method Description for details regarding the targeted gene regions evaluated by this test.

Reference Values

An interpretive report will be provided.

Interpretation

The interpretation of molecular biomarker analysis includes an overview of the results and the associated diagnostic, prognostic, and therapeutic implications.

Cautions

This test is not designed to differentiate between somatic and germline alterations. Additional testing may be necessary to clarify the significance of results if there is a potential hereditary risk.

A negative (wildtype) result does not rule out the presence of a rearrangement (fusion) that may be present but below the limits of detection of this assay. The analytical sensitivity of this assay is a minimum coverage of 10 targeted fusion reads with 5 unique fusion molecules in a sample with 10% or greater tumor content.

Only gene rearrangements (fusions) involving targeted regions in NTRK1, NTRK2, and NTRK3 genes will be detected. This test does not detect point mutations, insertion/deletion mutations, large single or multiexon deletions or duplications, or genomic copy number variants in any of the genes tested.

Rare alterations (ie, polymorphisms) may be present that could lead to false-negative or false-positive results.

Test results should be interpreted in the context of clinical findings, tumor sampling, and other laboratory data. If results obtained do not match other clinical or laboratory findings, contact the laboratory for an updated interpretation. Misinterpretation of results may occur if the information provided is inaccurate or incomplete.

Reliable results are dependent on adequate specimen collection and processing. This test has been validated on formalin-fixed, paraffin-embedded tissues; other types of fixatives are discouraged. Improper treatment of tissues, such as decalcification, may cause polymerase chain reaction failure.

Clinical Reference

1. Drilon A, Laetsch TW, Kummar S. Efficacy of Larotrectinib in TRK fusion-positive cancers in adults and children. N Engl J Med. 2018;378(8):731-739. doi:10.1056/NEJMoa1714448

2. Cocco E, Scaltriti M, Drilon A. NTRK fusion-positive cancers and TRK inhibitor therapy. Nat Rev Clin Oncol. 2018;15(12):731-747. doi:10.1038/s41571-018-0113-0

Method Description

Next-generation sequencing (NGS) is performed to test for the presence of fusions involving targeted regions in NTRK1, NTRK2, and NTRK3 genes. Fusion gene nomenclature is based on a custom reference sequence using genome build GRCh37 (hg19). See NTRK RNA Targeted Gene Fusions for details regarding the targeted gene regions identified by this test.(Unpublished Mayo method)

Day(s) Performed