Is a stable disease according to RECIST criteria a real stable disease in GIST patients treated with imatinib mesylate (IM) included in the intergroup EORTC/ISG/AGITG trial?

9510 Background: From 2/2001 to 2/2002, 946 patients (pts) with advanced GIST were randomized to IM at two dose levels within a controlled EORTC/ISG/AGITG trial. This analysis investigates whether achievement of an objective response, according to the RECIST criteria, has any predictive value for time to progression (TTP) and overall survival (OS). Methods: According to the protocol, the 3 first disease measurements were foreseen at 2, 4, and 6 months (m). Results of those measurements were classified in 6 categories: PR (>30% reduction of the tumor load), MR (10–30% reduction), NC- (0–10% reduction), NC+ (0–20% increase), PD (> 20% increase or new lesions), and subjective PD (clinical PD, no measurements). Pts included the analyses were those still followed at the measurement point, who had not previously progressed. Results: A total of 906 pts had measurable disease at entry; from those, 852 were evaluable at 2 m, 681 at 4 m and 642 at 6 m. At all measurement time points, PR and MR resulted in similar T...