Role for GIST genotyping stirs controversy
EXPERT ANALYSIS FROM SARCOMA AND GIST 2014
Based on current data for GIST sensitivity to TKIs, Dr. Trent and Dr. Demetri summarized the current GIST mutation and treatment landscape this way:
• About 60% of GIST have the most common tyrosine kinase mutation, in exon 11 of the KIT gene, and are sensitive to 400 mg/day of imatinib.
• About 7% of GIST have the exon 9 mutation of KIT and are sensitive to a higher dosage of imatinib, ideally 800 mg/day if that is tolerated.
• About 20% of GIST have the D842V mutation in the PDGFRA tyrosine kinase gene, and these patients are candidates for enrollment in a trial, as no regimens are known effective for these tumors.
• About 12% of GIST have a mutation in the SDF gene, which appears to make them resistant to imatinib and sunitinib but which may be sensitive to another TKI, regorafenib.
• The remaining GIST have other, rare mutations.
Dr. Trent said that he had no disclosures. Dr. Demetri said that he has been a consultant to Bayer, Novartis, and other companies. Dr. Maki said that he has been a consultant to Eisai/Morphotek, Bayer, and other companies, and has received research support from Eisai/Morphotek, Tracon, and Bayer. Dr. Benjamin said that he has been a consultant to Johnson & Johnson, Merck, and Pfizer.
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