Follow-up results after 9 years (yrs) of the ongoing, phase II B2222 trial of imatinib mesylate (IM) in patients (pts) with metastatic or unresectable KIT+ gastrointestinal stromal tumors (GIST).

10016 Background: B2222 was the first large trial to show that 1st-line IM induces high objective response rates and durable disease control in pts with advanced GIST. Sequential study extensions allowed for ongoing IM treatment and extended pt follow-up, enabling evaluation of long-term survival and potential markers of disease control. Methods: Pts with advanced KIT+GIST were enrolled in an open-label, multicenter trial and randomized 1:1 to receive 400 or 600 mg/d IM. The original 3-yr study was serially extended to treat pts, who continued IM for >10 yrs, and to monitor long-term overall survival (OS) and progression-free (TTP) rates. Results: Of 147 pts initially enrolled between July 2000 and April 2001, 56 continued IM therapy beyond 3 yrs. Maximum follow-up time for this analysis was 9.9 yrs (median 9.4 yrs). As of May 26, 2010, 26 pts (17.7%) remained on continuous IM since study entry; the GIST genotypes were: KIT exon 11 mutant (m), n=16; KIT exon 9 m, n=3; PDGFRA m, n=1; wild type, n=1; and un...