CT Evaluation of the Response of Gastrointestinal Stromal Tumors After Imatinib Mesylate Treatment: A Quantitative Analysis Correlated with FDG PET Findings

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Abstract
OBJECTIVE. We correlated changes in tumor density on CT with changes in glucose metabolism, or the maximum standardized uptake value (SUVmax), on FDG PET and sought to develop CT imaging criteria that can be used to objectively evaluate tumor response in patients with metastatic gastrointestinal stromal tumors (GISTs) who undergo treatment with imatinib mesylate.MATERIALS AND METHODS. Using the criteria established by the Response Evaluation Criteria in Solid Tumors (RECIST) group, we selected 173 tumors (in 36 patients) for study. Tumor size and density were determined objectively, and overall tumor response (OTR) was evaluated subjectively on CT images. The changes in these parameters before and after treatment were correlated with changes in SUVmax.RESULTS. Significant decreases were seen in both tumor density (mean, 12.3 H [16.5%]; p < 0.0001) and SUVmax (mean, 3.43 [64.9%]; p < 0.0001). OTR evaluated subjectively, correlated well with changes in SUVmax (p < 0.0001). No statistically significant assoc...