Comparison of volumetric methods for tumor measurements on two and three dimensional MRI in adult glioblastoma

Change in tumor size is a frequent endpoint in cancer clinical trials, but whether change in size should be measured using volume on two-dimensional (2D) or three-dimensional (3D) images is not certain. We compared volumetric measurements on post-contrast 2D and high-resolution 3D T1-weighted MR images (T1WI) in evaluating tumor response in glioblastoma multiforme (GBM). Tumor volume measurements were performed on 86 MRI studies from 37 adult patients with GBM on post-contrast 5 mm 2D T1WI and isotropic high-resolution T1WI. The means of the two volumes were compared and their association was analyzed. There is no significant difference between volumes measured on 2D and 3D in 86 scans (Z=0.63, p=0.53), and a high correlation was revealed between them (r=0.95, 95% CI: 0.93-0.97, p < 0.001). When the percentage changes were categorized into traditional tumor response criteria (complete response/partial response/stable disease/progressive disease), the kappa coefficient between the volume on 2D and volume on 3D was 0.80 (95% CI: 0.57-1.03, p<0.05) with an overall agreement of 84%. Volume on post-contrast 2D T1WI appears comparable to volume on 3D T1WI and should be a practical alternative to volume on 3D in evaluating tumor response. (orig.)