• Christopher L Corless, Karla V Ballman, Cristina R Antonescu, Violetta Kolesnikova, Robert G Maki, Peter W T Pisters, Martin E Blackstein, Charles D Blanke, George D Demetri, Michael C Heinrich, Margaret von Mehren, Shreyaskumar Patel, Martin D McCarter, Kouros Owzar, and Ronald P DeMatteo.
• Christopher L. Corless, Violetta Kolesnikova, Charles D. Blanke, Michael C. Heinrich, Oregon Health and Science University, Portland, OR; Karla V. Ballman, Mayo Clinic, Rochester, MN; Cristina R. Antonescu and Ronald P. DeMatteo, Memorial Sloan-Kettering Cancer Center; Robert G. Maki, Mt Sinai School of Medicine, New York, NY; Peter W.T. Pisters and Shreyaskumar Patel, University of Texas MD Anderson Cancer Center, Houston, TX; Martin E. Blackstein, Mount Sinai Hospital, Toronto, Ontario, Canada; George D. Demetri, Dana-Farber Cancer Institute, Boston, MA; Margaret von Mehren, Fox Chase Cancer Institute, Philadelphia, PA; Martin D. McCarter, University of Colorado School of Medicine, Aurora, CO; and Kouros Owzar, Duke University School of Medicine, Durham, NC. corlessc@ohsu.edu.
• J. Clin. Oncol. 2014 May 20; 32 (15): 1563-70.

PurposeThe ACOSOG (American College of Surgeons Oncology Group) Z9001 (Alliance) study, a randomized, placebo-controlled trial, demonstrated that 1 year of adjuvant imatinib prolonged recurrence-free survival (RFS) after resection of primary GI stromal tumor (GIST). We sought to determine the pathologic and molecular factors associated with patient outcome.Patients And MethodsThere were 328 patients assigned to the placebo arm and 317 to the imatinib arm. Median patient follow-up was 74 months. There were 645 tumor specimens available for mitotic rate or mutation analysis.ResultsRFS remained superior in the imatinib arm (hazard ratio, 0.6; 95% CI, 0.43 to 0.75; Cox model-adjusted P < .001). On multivariable analysis of patients in the placebo arm, large tumor size, small bowel location, and high mitotic rate were associated with lower RFS, whereas tumor genotype was not significantly associated with RFS. Multivariable analysis of patients in the imatinib arm yielded similar findings. When comparing the two arms, imatinib therapy was associated with higher RFS in patients with a KIT exon 11 deletion of any type, but not a KIT exon 11 insertion or point mutation, KIT exon 9 mutation, PDGFRA mutation, or wild-type tumor, although some of these patient groups were small. Adjuvant imatinib did not seem to alter overall survival.ConclusionOur findings show that tumor size, location, and mitotic rate, but not tumor genotype, are associated with the natural history of GIST. Patients with KIT exon 11 deletions assigned to 1 year of adjuvant imatinib had a longer RFS.© 2014 by American Society of Clinical Oncology.

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