Test Catalog

Test ID: GISTP    
GIST-Targeted Gene Panel by Next-Generation Sequencing, Tumor

Useful For Suggests clinical disorders or settings where the test may be helpful

Diagnosis and management of patients with gastrointestinal stromal tumors

Genetics Test Information Provides information that may help with selection of the correct genetic test or proper submission of the test request

This test uses targeted next-generation sequencing to evaluate for somatic mutations within the KIT (exon 2, 9, 10, 11, 13, 14, 15, 17, 18) and PDGFRA (exons 12, 14, 15, 18) genes. See Targeted Gene Regions Interrogated by Solid Tumor Targeted Cancer Gene Panel by Next-Generation Sequencing in Special Instructions for details regarding the targeted gene regions identified by this test.

 

Of note, this test is performed to evaluate for somatic mutations within solid tumor samples. This test is not intended for use for hematological malignancies. Additionally, this test does not assess for germline alterations within the genes listed.

Testing Algorithm Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

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

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

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 United States Food and Drug Administration (FDA) 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.

 

Next-generation sequencing has recently emerged as an accurate, cost-effective method to identify mutations across numerous genes known to be associated with response or resistance to specific targeted therapies. This test is a single assay that uses formalin-fixed paraffin-embedded tissue to assess for common mutations in the KIT and PDGFRA genes known to be associated with gastrointestinal stromal tumors (GIST). The results of this test can be useful for assessing prognosis and guiding treatment of individuals with GIST.

 

See Targeted Gene Regions Interrogated by Solid Tumor Targeted Cancer Gene Panel by Next Generation Sequencing in Special Instructions for details regarding the targeted gene regions identified by this test.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

An interpretative report will be provided.

Interpretation Provides information to assist in interpretation of the test results

An interpretive report will be provided.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

This test cannot differentiate between somatic and germline alterations. Additional testing may be necessary to clarify the significance of results if there is a potential hereditary risk. DNA variants of uncertain significance may be identified.

 

A negative (wild-type) result does not rule out the presence of a mutation that may be present but below the limits of detection of this assay (approximately 5%-10%). This test does not detect large single or multiexon deletions or duplications or genomic copy number variants.

 

Rare 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, please contact the laboratory for 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 PCR failure.

 

KIT mutations can be seen in neoplasms other than gastrointestinal stromal tumors including, but not limited to: mast cell disease, melanoma, seminomas, acute myeloid leukemia, myeloproliferative neoplasms, and some lymphomas.

 

PDGFRA mutations may be occasionally found in inflammatory fibroid polyps.(1)

Supportive Data

We studied a set of 75 formalin-fixed, paraffin-embedded specimens: 40 classic gastrointestinal stromal tumors (GIST), 10 unrelated tumors, 21 neuroendocrine tumors, and 4 other tumors (2 metastatic melanomas, 1 breast cancer, and 1 squamous cell carcinoma). The literature reports that approximately 80% of GISTs harbor a mutation in KIT gene, while 2% to 5% harbor mutations in PDGFRA. Overall, we found 83% of GISTs tested demonstrated mutations in KIT and/or PDGFRA, which is in accordance with the literature.

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. Schildhaus HU, Cavlar T, Binot E, et al: Inflammatory fibroid polyps harbour mutations in the platelet-derived growth factor receptor alpha (PDGFRA) gene. J Pathol 2008;216(2):176-182

2. Robson ME, Blogowski E, Sommer G, et al: Pleomorphic characteristics of a germ-line KIT mutation in a large kindred with gastrointestinal stromal tumors, hyperpigmentation, and dysphagia. Clin Cancer Res 2004;10:1250-1254

3. Li FP, Fletcher JA, Heinrich MC, et al: Familial gastrointestinal stromal tumor syndrome: phenotypic and molecular features in a kindred. J Clin Oncol 2005;23:2735-2743

4. Corless CL, Fletcher JA, Heinrich MC: Biology of gastrointestinal stromal tumors. J Clin Oncol 2004;22:3813-3825

5. Debiec-Rychter M, Raf Sciot R, Le Cesne A, et al: KIT mutations and dose selection for imatinib in patients with advanced gastrointestinal stromal tumors. Eur J Cancer 2006;42:1093-1103

6. Heinrich MC, Corless CL, Demetri GD, et al: Kinase mutations and imatinib mesylate response in patients with metastatic gastrointestinal stromal tumor. J Clin Oncol 2003;21:4342-4349

7. Debiec-Rychter M, Dumez H, Judson I, et al: Use of c-KIT/PDGFRA mutational analysis to predict the clinical response to imatinib in patients with advanced gastrointestinal stromal tumors entered on phase I and II studies of the EORTC Soft Tissue and Bone Sarcoma Group. Eur J Cancer 2004;40:689-695

Special Instructions Library of PDFs including pertinent information and forms related to the test