Abstract
10052 Background: The aim of the study was to assess the outcomes of imatinib (IM) therapy in subgroup of patients with advanced CD117(+) GIST originating from small intestine. Methods: In the group of 245 consecutive patients with inoperable and/or metastatic GIST CD117(+) treated with imatinib in the dose of 400–800mg daily and enrolled into prospectively collected Clinical GIST Registry between 09/2001 and 10/2006 we identified 123 patients (50.2%) with GIST originating from small bowel. There were 43 primary unresectable/metastatic tumors and 80 recurrent (after primary surgery) tumors. Median follow-up time was 31 months (range: 3–63). Results: The estimated 3-year progression-free survival (PFS; calculated form the date of the start of IM) and overall survival (OS) were 61% and 80%, respectively. The best responses observed during IM therapy according to RECIST criteria were as follows: complete responses (CRs) - 9 cases (7%), partial responses (PRs) - 66 cases (54%), stable disease SD - 29 cases (24%) and progressive disease (PD) - 19 (15%). In 42 analyzed specimens 29 GISTs (69%) had exon 11 KIT mutations, 9 (21%) - exon 9 KIT mutations and 4 (10%) other genetic abnormalities. We identified three factors negatively affecting PFS statistically significant (p<0.05) in multivariate analysis: baseline poor WHO performance status = 2, tumor genotype with other than exon 11 KIT mutant and primary tumor mitotic index >10/50HPF. Two more additional factors had negative impact on PFS in univariate analysis only: baseline high neutrophil count (p=0.04) and low baseline hemoglobin level (p=0.01). Conclusions: In analysis of the subset of patients with advanced GIST originating from the small bowel we confirmed long-term benefit from IM therapy. We identified three independent biological factors influencing the progression-free survival during imatinib therapy in this group of patients. [Table: see text]
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