Treatment response monitoring in patients with gastrointestinal stromal tumor using diffusion-weighted imaging: preliminary results in comparison with positron emission tomography/computed tomography

We compared the parameters derived from diffusion-weighted imaging (DWI) and positron emission tomography/computed tomography (PET/CT) for treatment response evaluation and response prediction in patients with gastrointestinal stromal tumor (GIST). Seven patients with histologically proven metastatic disease were enrolled. DWI and PET/CT data were collected from all patients at diagnosis and from six at follow-up. All 37 lesions were identifiable in DWI with a sensitivity of 100%. To achieve higher accuracy, we used the apparent diffusion coefficient (ADC) of liver and background noise as thresholds for the measurement of the ADCs of lesions. Significant inverse correlations were found between ADCmean_thr (ADCmean with thresholds) and SUVmean (mean standardized uptake value) (R2 = 0.523, p < 0.001 at diagnosis, and R2 = 0.916, p < 0.001 at follow-up), between ADCmean_thr and SUVmax (maximum SUV) (R2 = 0.529, p < 0.001 at diagnosis, and R2 = 0.761, p < 0.001 at follow-up), between ADCmean_thr (percentage change in ADCmean_thr) and SUVmean (percentage change in SUVmean) (R2 = 0.384, p < 0.001), and between ADCmean_thr and SUVmax (percentage change in SUVmax) (R2 = 0.500, p < 0.001). In lesion-based analysis, pre-treatment ADCmean_thr outperformed SUVmean and SUVmax in treatment response prediction, with an area under the receiver operating characteristic curve of 0.706. These results show that DWI can provide a quantitative assessment comparable with PET/CT in GIST lesion characterization, treatment response evaluation and response prediction. Copyright (c) 2012 John Wiley & Sons, Ltd.