Learn about various mutation types. There are several types of gene mutations that can lead to Gastrointestinal Stromal Tumors. These include KIT mutations, PDGFRA mutations and BRAF and SDH mutations. As each of these involves different genes, the course of the disease and the treatments can vary. That is why gene mutation screening is so important for individuals who have been diagnosed with GIST.
The type and location of these mutations has proven to be a strong predictor of how a patient will respond to treatment with targeted drugs such as Gleevec and Sutent.
About 75% of GISTs have a mutation in the gene encoding KIT tyrosine kinase, while about 5% to 8% have a mutation in the related kinase PDGFRA. About 15% do not have identifiable gene mutations, and include those categorized as “wild-type” GIST.
Testing for mutations in the KIT and PDGFRA genes is available through the Molecular Diagnostics Laboratory of Oregon Health & Science University and in several other labs around the country. For a list of testing centers, see below. For GIST patients with prior surgery the test requires a tissue sample from the hospital where the surgery was performed. It is then sent to one of the labs. In some cases where there was no surgery, a biopsy sample may still have adequate tissue to perform the test.
Testing is typically performed in several stages. KIT exons 9 and 11 are screened first, as about 75% of GISTs will have a mutation in one of these two exons. An exon is the part of the gene containing coding information. KIT exons 13 and 17 and PDGFRA exons 12 and 18 are screened next. If no mutations are found in these exons, the tumor is presumed to be wild-type.
Testing for SDH and BRAF mutations are not yet part of a standard mutational test. BRAF testing is available through both Oregon Health Sciences University and Memorial Sloan Kettering Cancer Center. SDH testing is available from the National Institutes of Health.
Treatment decisions may be influenced by the type of gene mutation. Patients with GISTs with an exon 11 mutation have better responses to the drug Gleevec and better overall survival than those with exon 9 mutations. GISTs with exon 9 mutations have a lower response rate to Gleevec therapy when compared to exon 11 mutations and they seem to require a higher dosage of Gleevec. With the appropriate higher dose, the response of exon 9 patients tends to approach that of exon 11 patients. Exon 9 patients also seem to respond fairly well to the second-line drug Sutent. As many as two-thirds of PDGFRA mutations do not respond to these drugs. For wild-type GIST, Sutent may provide more benefit and there are anecdotal reports of benefit with Tasigna.
Despite a cancer task force recommendation that metastatic and high-risk GIST patients do mutational screening, only about 8% of GIST patients in the United States are tested. The Life Raft Group is working to encourage mutational screening for GIST patients.
Other Mutational Testing Sites:
|Dr. Carlos Barrios
Department of Oncology,
Centro da Obesidade Mórbida
Hospital São Lucas da PUCRS,
Porto Alegre, Brazil
|Progenetica Diagnosticos Moleculares
Dr. Carlos Gil Ferreira
Progenetica Diagnosticos Moleculares
Rua Jardim Botânico, 700 sala 613
Rio de Janeiro- RJ
22461-000Phone: 55 21 2540 5529
|Cross Cancer Institute, Alberta Canada
Dr. Raymond Lai/ Angie Battochio
Dept. of Lab Medicine and Pathology
Cross Cancer Institute
11560 University Ave.
Edmonton, Alberta Canada
T6G 1Z2Phone: 780-432-8338
Dr. Raymond Lai: email@example.com
|Centre Hospitalier de l’Université de Montréal
Montréal, Quebec, Canada (for Canadian citizens)
|National University Hospital, Singapore
A/Prof Manuel Salto-Tellez
Department of Pathology
Histopathology Receiving Section, Room #03-204
National University Hospital
5 Lower Kent Ridge Road
Republic of SingaporePhone: 65-67724704
C/ Poeta Rafael Morales 2
28702 San Sebastián de los Reyes
Madrid – SpainTlf. +34 91 659 22 98
Fax +34 91 659 22 99E-mail: firstname.lastname@example.org
|Dr. Kyoung-Mee Kim
Samsung University Medical Center
|Mackay Memorial Hospital, Taiwan
Dr. Tzen/ Vivian Chang
Mackay Memorial Hospital
Department of Pathology
45 Minsheng Road
Tamshui, Taipei 251, TaiwanDr. Chin-Yuan Tzen: email@example.com
Vivian Chang MS: firstname.lastname@example.org
|Chulalongkorn University, Thailand
Dr. Virote Sriuranpong
Medical Oncology Unit, Dept. of Medicine
Faculty of Medicine, Chulalongkorn University
4th Floor Vongvanich Building
Rama IV Rd, Ptumwan
Bangkok, Thailand 10330Phone: 662-256-4533
Dr. Virote Sriuranpong: email@example.com
|Dr. Lawrence Weiss
City of Hope
Molecular Diagnostic Laboratory (MDL)
1500 E. Duarte Rd.
Duarte, CA 91010
|Spencer Green MS M BAHA
UCD Department of Pathology SCW
Phone: 303 724-3707
Mail Stop B216
12631 E. 17th Ave
Aurora, CO 80045
|Dr. David Klinstra
Chief of Surgical Pathology Services
Memorial Sloan Kettering Hospital-
1275 York Avenue
New York, New York 10065
Phone: 212 639 2410
|Fox Chase Pathology Dept.
Dr. Harry Cooper
Phone: 215 728-3675
333 Cottman Ave.
Philadelphia, PA 19111
|MD Anderson Cancer Center
Contact: Jon Trent, MD
*Testing can only be done with patients
who go to MD Anderson
Salt Lake City, Utah