Solid Tumors cKIT-GIST (may include exons 9,11,13,17) Mutation Analysis, reflexed to PDGFRA

Approximately 80% of gastrointestinal stromal tumors (GISTs) have an oncogenic mutation in the gene encoding KIT tyrosine kinase.¹  Another 5-7% of GISTs have a mutation in the gene encoding the related kinase PDGFRA (platelet-derived growth factor receptor alpha).¹  KIT and PDGFRA mutations are mutually exclusive in GISTs.  In both genes, the observed mutations are invariably in-frame and result in expression of a mutant kinase isoform that has constitutive tyrosine kinase activity. Approximately 10-15% of GISTs have no detectable KIT or PDGFRA gene mutation.

Screening for kinase mutations in suspected GISTs can be helpful for the following reasons.

• The presence of a mutation provides molecular confirmation of the diagnosis.
• Clinical response to treatment withimatinib mesylate (GleevecTM) is predicted by the kinase mutation status, as detailed in the table below.
• The progression-free survival of patients with KIT exon 9-mutant GIST is significantly longer when they are treated with 800mg/d imatinib as opposed to 400mg/d.2  In contrast, the PFS of patients with KIT exon 11-mutant tumor is not influenced by drug dosage.

 Mutation Status*

^#Defined as complete or partial response by RECIST criteria.

*Compilation of data from the SWOG S0033 and EROTC phase III trials of imatinib for advanced GIST.^2,3

Similar data were previously published from phase II trials.^4,5

The testing protocol involves the following steps

1. Microscopic examination of the specimen and macrodissection of tumor-rich areas.
2. DNA extraction and purification.
3. PCR amplification of selected KIT exons, serially in this order: exon 11, 9, 13 & 17.
4. Screening for mutations by one of two methods: direct, bidirectional sequencing, or real-time PCR with high resolution melting curve analysis.  DNA sequencing is used to confirm any mutations picked up by melting curve analysis.
5. The estimated sensitivity of these methods is 20% mutant allele. 
6. If KIT mutations are not detected, the specimen wil be reflexed to PDGFRA and appropriate testing charges will be incurred. Please see PDGFRA Information Sheet for Methodology.

• A paraffin block or
• 10 unstained sections of tumor (4-5 microns)(15 sections for small biopsies)

Contact Client Services for shipping materials and procedures at 855-535-1522

A REQUISITION FORM MUST ACCOMPANY ALL SAMPLES.  Please include detailed clinical information.

Mon - Fri

10 - 14 days

• Keep specimen cool during transit. Do not ship on dry ice.
• Please use the cold pack provided in the KDL shipping kit.
• Ship the specimen overnight express, using the FedEx priority overnight label provided. 

Contact Client Services for shipping materials and procedures at 855-535-1522.

1. Corless CL, Fletcher JA, Heinrich MC. Biology of gastrointestinal stromal tumors. J Clin Oncol 22:3813-3825, 2004.
2. Debiec-Rychter M, Sciot R, Le Cesne A, Schlemmer M, Hohenberger P, van Oosterom AT, Blay J-Y, Leyvraz S, Stul M, Casali PG, Zalcberg J, Verweij J, Van Glabbeke M, Hagemeijer A, Judson I. KIT mutations and dose selection for imatinib in patients with advanced gastrointestinal stromal tumours. Eur J Cancer 42:1093-103, 2006.
3. Heinrich MC, Owzar K, Corless CL, Hollis D, Borden EC, Fletcher CD, Ryan CW, von Mehren M, Blanke CD, Rankin C, Benjamin RS, Bramwell VH, Demetri GD, Bertagnolli MM, Fletcher JA. Correlation of kinase genotype and clinical outcome in the North American Intergroup Phase III trial of imatinib mesylate for treatment of advanced gastrointestinal stromal tumor: CALGB 150105 Study by Cancer and Leukemia Group B and Southwest Oncology Group. J Clin Oncol 26:5360-7, 2008.
4. Heinrich MC, Corless CL, Demetri GD, Blanke CD, von Mehren M, Joensuu H, McGreevey LS, Chen C-J, Kiese B, Eisenberg B, Roberts PJ, Singer S, Fletcher CDM, Silberman S, Dimitrijevic S, Fletcher JA.  Kinase mutations and imatinib mesylate response in patients with metastatic gastrointestinal stromal tumor. J Clin Onc 21:4342-4349, 2003.
5. Debiec-Rychter M, Dumez H, Judson I, Wasag B, Verweij J, Brown M, Dimitrijevic S, Sciot R, Stul M, Vranck H, Scurr M, Hagemeijer A, Van Glabbeke M, Van Oosterom AT. Use of c-KIT/PDGFRA mutational analysis to predict the clinical response to imatinib in patients with advanced gastrointestinal stromal tumours entered on phase I and II studies of the EORTC Soft Tissue and Bone Sarcoma Group. Eur J Cancer 40:689-95, 2004