Myelodysplastic syndromes developing after imatinib therapy for GIST

10532 Background: Imatinib mesylate 400 mg a day is the standard treatment for patients (pts.) who have advanced or metastatic gastrointestinal stromal tumor (GIST) even if different kit and PDGFRA mutations have a marked impact on the outcome of pts.; briefly, pts. with exon 9 mutations fared worse than those who had exon 11 mutations and both types of pts. did better than those with wild type genotype. Previously, we had detected clonal chromosomal abnormalities in the bone marrow of GIST pts. who developed a myelodysplastic syndrome during treatment with imatinib, so we performed a systematic study in a series of male and female GIST pts. during treatment with imatinib. Methods: Between January 2007 and December 2008, bone marrow samples for morphologic analysis, FISH and classical cytogenetics were obtained from 49 pts. (30 male; 19 female, mean age 62) with unresectable or metastatic GIST before and during treatment with 400 mg/d of imatinib. For pts. with progressive disease (15 pts.) or exon 9 muta...