Comparison of performance of various tumor response criteria in assessment of sunitinib activity in advanced gastrointestinal stromal tumors.

Purpose: To compare the performance of various tumor response criteria (TRC) in the assessment of patients with advanced gastrointestinal stromal tumor (GIST) treated with sunitinib after failure of imatinib.

Methods: Sixty-two participants with advanced GIST in two clinical trials received oral sunitinib after prior failure of imatinib (median duration 24 weeks; interquartile range 14-56) and were followed with contrast-enhanced computed tomography at baseline and thereafter at median intervals of 6 weeks (IRQ 6-9). Tumor response was prospectively determined using Response Evaluation Criteria in Solid Tumors (RECIST) 1.0, and retrospectively reassessed for comparison using RECIST 1.1, Choi criteria, and modified Choi (mChoi) criteria using the original target lesions. For mChoi criteria, progressive disease was defined as 20% increase in sum of the longest dimension, similar to RECIST 1.1. Clinical benefit rate (CBR; complete response, partial response, or stable disease ≥12 weeks) and progression-free survival were compared between various TRCs using kappa statistics.

Results: While partial response as the best response was more frequent by Choi and mChoi criteria (50% each) than RECIST 1.1 (15%) and RECIST 1.0 (13%), CBR was similar between various TRCs (overall CBR 60%-77%, 77%-94% agreement between all TRC pairs). Time to best response was shorter for Choi and mChoi criteria (median 11 weeks each) compared to RECIST 1.1 and RECIST 1.0 (median 25 and 24 weeks, respectively). PFS was similar for RECIST 1.1, RECIST 1.0, and mChoi (median 35 weeks each), and shortest for Choi criteria (median 23 weeks).

Conclusions: CBR was similar among the various TRCs, although Choi criteria led to earlier determination of disease progression. Therefore, RECIST 1.1 and mChoi criteria may be preferred for response assessment in patients with advanced GIST.