Kinase Genotyping of Gastrointestinal Stromal Tumors (GIST) From Patients Enrolled in the A6181112 Phase IIIb Trial at Participating U.S. and Ex-U.S. Medical Centers

In this companion study, we will analyze the genomic DNA from the GIST tumor specimens of patients enrolled in the in the A6181112 phase IIIb trial at participating U.S. and ex-U.S. medical centers. Specifically, GIST samples will be screened for mutations in KIT gene exons 9, 11, 13 and 17, and PDGFRA gene exons 12, 14 and 18, to determine the primary kinase genotype. Subset analyses will be performed and compared with the overall PFS rates observed in patients with primary and secondary imatinib resistance. Based on data from a previous phase I/II trial, our hypothesis is that patients with either primary or secondary imatinib resistance having a KIT exon 9-mutant or WT GIST will have a longer PFS when treated with sunitinib than patients with exon 11-mutant GIST. We further hypothesize that this difference will be observed among patients treated with high-dose imatinib.