Hamid Reza Dabirzadeh MD, Presenter: Nothing to Disclose

Thanh Nguyen MD, Abstract Co-Author: Research grant, Bayer AG

Jean-Michel Caudrelier MD, Abstract Co-Author: Nothing to Disclose

John Sinclair, Abstract Co-Author: Nothing to Disclose

John Woulfe MD, Abstract Co-Author: Nothing to Disclose

To measure relative cerebral blood volume (rCBV) and K2 (a measurement of contrast leakage) in patients with previously resected glioblastoma multiforme (GBM) who have progressively enlarging enhancing lesions and to correlate the results with post operative histopathological findings.

In a retrospective cohort of 50 patients with GBM treated with surgery followed by radiation therapy plus concomitant adjuvant Temozolamide, we identified 17 patients with progressively enlarging enhancing lesions on MRI who had reresection of their tumor.  MR T2*perfusion was performed using a dose of 0.1 mmol/kg of Magnevist injected at 4 cc/s at 1.5 T or 3T. The patient’s immediate preoperative MR perfusion images were processed using NordicICE perfusion.  rCBV and K2 were measured by placing regions of interest (ROIs) on the enhancing lesions. Following reresection of the lesions, the pathologist visually estimated the percentage of necrosis and tumor recurrence in the resected specimens. Patients were then divided into two groups: one with less than 50% radiation necrosis (10 patients) and one with more than 50% tumor necrosis (7 patients). A non-parametric t-test (Wilcoxon Rank Sum) was performed to compare normalized rCBV and K2 values from the two groups. Regression analysis was performed to determine the relationship between K2 and % radiation necrosis.

For K2 values, the mean for the 1st group (<50% radiation necrosis) was 0.40 (95% CI -0.054-0.85) and the mean for the 2nd group (>50% radiation necrosis)was 0.99 (95% CI 0.33-1.65).  This difference was not statistically significant (p=0.13).  There was a linear relationship between K2 and % radiation necrosis (r=0.28 95% CI 0.11-0.46, p=0.03). For rCBV values normalized to the contralateral normal white matter, the mean for the 1st group  was 1.82 (95% CI  1.33-2.31) and the mean for the 2nd group was 2.04 (95% CI  0.51-3.57).  This difference was not statistically significant (p=0.6).       

In this pilot study, we could not find a difference of rCBV between patients treated for GBM with <50% radiation necrosis and those with >50% radiation necrosis.  The K2 values for patients with <50% radiation necrosis were lower than for patients with >50% radiation necrosis but this was not statistically significant.  

K2 values might help identify radiation necrosis in patients with treated GBM.

Dabirzadeh, H, Nguyen, T, Caudrelier, J, Sinclair, J, Woulfe, J, Differentiation of Radiation Necrosis from Recurrent Tumor in Patients with GBM Using T2 Perfusion MRI.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11034543.html