title: 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.
abstract: OBJECTIVE
  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.
  
  
  CONCLUSIONS
  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.
authors: Institute of Clinical Radiology and Nuclear Medicine, University Medical Center Mannheim, Medical Faculty Mannheim, Heidelberg University, Theodor-Kutzer-Ufer 1-3, D-68167 Mannheim, Germany. mr.meyer.mathias@gmail.com
authors: M
authors: M
authors: Meyer
authors: P
authors: P
authors: Hohenberger
authors: P
authors: P
authors: Apfaltrer
authors: T
authors: T
authors: Henzler
authors: D J
authors: DJ
authors: Dinter
authors: S O
authors: SO
authors: Schoenberg
authors: C
authors: C
authors: Fink
mesh_terms: D000328:Adult; D000368:Aged; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D005260:Female; D005770:Gastrointestinal Neoplasms / Q000000981:diagnostic imaging* / Q000188:drug therapy*; D046152:Gastrointestinal Stromal Tumors / Q000000981:diagnostic imaging* / Q000188:drug therapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors*; D015900:Radiography, Dual-Energy Scanned Projection / Q000379:methods; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*; D016896:Treatment Outcome
chemical_list: D000970:Antineoplastic Agents; D011505:Protein-Tyrosine Kinases