NI-74 * DYNAMIC CONTRAST ENHANCED (DCE) T1 MRI PERFUSION DIFFERENTIATES PSEUDOPROGRESSION FROM RECURRENT GLIOBLASTOMA

Abstract

PURPOSE: Pseudoprogression may present as transient new or increasing enhancing lesion(s) that mimics recurrent tumor in patients treated for glioblastoma. The purpose of this study was to examine the utility of DCE-MRI in differentiating between pseudoprogression (PsP) and tumor progression (POD). METHODS: We retrospectively examined consecutive patients with glioblastoma, who developed new and/or increasing enhancing lesion(s) after chemoradiation. Axial contrast T1-weighted images and DCE MRI data were analyzed using Nordic Ice (NordicNeuroLabs, Milwaukee, WI) in a blinded fashion. After semiautomated arterial input function selection, plasma volume (Vp) and time-dependent leakage constant (Ktrans) maps were calculated. A volume of interest was drawn around the enhancing lesion on the contrast T1-weighted images and transferred onto the Vp and Ktrans maps. The measurements were binned, and histogram analysis was performed. Pseudoprogression was defined as stable disease not requiring new treatment for a minimum of 3 months, or by surgical pathology if available. Wilcoxon rank-sum tests were performed on normalized ratios and p set to 0.05. RESULTS: Fifty patients with newly diagnosed glioblastoma treated with standard chemoradiation were included. The mean age was 64 years (66 PsP, 64 POD), and median KPS was 82 (90 PsP, 80 POD). Patients with PsP (n = 13, 26%) had Vp(mean) = 2.64, Vp(75%tile) = 2.80; and Ktrans(mean) = 3.29 and Ktrans(75%tile) = 3.40. Patients with POD (n = 37, 74%) had Vp(mean) = 6.47, Vp(75%tile) = 6.79; and Ktrans(mean) = 7.77 and Ktrans(75%tile) = 8.55. PsP demonstrated significantly lower Vp (p <0.0005), as well as significantly lower Ktrans (p <0.005). MGMT promoter hypermethylation was present in 7 of 12 patients with PsP (58.3%). Median overall survival was 13.8 months (PsP 17.7 months, 11 patients alive; POD 12.6 months, 13 alive). CONCLUSION: DCE MRI shows lower perfusion in pseudoprogression than in tumor progression. This suggests that DCE MRI has a role in triaging glioblastoma patients with indeterminate enhancing lesions following treatment to help make better informed therapeutic decisions.