CT-based response assessment of advanced gastrointestinal stromal tumor: Dual energy CT provides a more predictive imaging biomarker of clinical benefit than RECIST or Choi criteria

Objectives: Dual-energy CT (DECT) allows quantification of intravenously injected iodinated contrast media in tumors, and therefore may be considered as a surrogate marker for perfusion and tumor vascularity. This study evaluated whether newly developed DECT response criteria allow better correlation with survival than established response criteria. Methods: Seventeen patients with advanced GIST treated with tyrosine-kinase-inhibitors were assessed by contrast-enhanced DECT 2 and 6 months after beginning of treatment. Response to treatment of 165 tumor lesions was evaluated according to RECIST, Choi criteria and newly developed DECT criteria, defining non-responders as an increase of both tumor size >20% and iodine related attenuation or either a >50% increase of tumor size or iodine related attenuation. All other patients were classified as responders. Progression-free survival (PFS) and overall survival (OS) were calculated by Kaplan-Meier analysis. Results: Choi criteria and DECT showed a significantly longer median PFS of patients rated as responders than patients rated as non-responders (9-29 months vs. 2-6 months; p < 0.02) at follow-up. Only DECT analysis at 6 months follow-up allowed a valid prediction of OS. Conclusion: This study indicates that DECT allows a better prediction of therapeutic benefit in advanced GIST patients treated with tyrosine-kinase-inhibitors than established response criteria. However, the most important predictive biomarker of therapeutic benefit was absence of progression, no matter which response evaluation criteria were applied. (C) 2013 Elsevier Ireland Ltd. All rights reserved.