T1-Weighted Dynamic Contrast-Enhanced MR Perfusion Imaging Characterizes Tumor Response to Radiation Therapy in Chordoma

Abstract

Background and Purpose Chordomas notoriously demonstrate a paucity of changes following radiation therapy on conventional MRI. We hypothesize that dynamic contrast enhanced (DCE) MR perfusion imaging parameters of chordomas would change significantly following radiation therapy. Materials and Methods Eleven pathology-proven chordoma patients who completed DCE MR perfusion imaging pre -and post-radiation therapy were enrolled. Quantitative tumor measurements were taken by two attending neuroradiologists. ROIs were used to calculate vascular permeability (Ktrans) and plasma volume (Vp), and generate dynamic contrast enhancement curves. Quantitative analysis was performed to determine mean and maximum Vp and Ktrans values, while semi-quantitative analysis on averaged concentration curves was used to determine the area under the curve (AUC). A Mann-Whitney U test at a significance level of p<0.05 was used to assess differences of above parameters between pre- and post-radiation therapy. Results Vp mean (pre-treatment μ=0.82, post-treatment μ=0.42), Vp maximum (pre- treatment μ=3.56; post- treatment μ=2.27), and Ktrans mean (pre- treatment μ=0.046; post- treatment μ=0.028) in the ROIs significantly decreased after radiation therapy (p<0.05), thereby demonstrating potential for assessing tumor response. AUC values also demonstrated significant differnces (p<0.05). Conclusions Vp and Ktrans, decreased after radiation therapy, suggesting that these DCE-MR perfusion parameters may be useful for monitoring chordoma growth and response to radiation therapy. Additionally, the characteristic dynamic MR signal intensity time curve of chordoma may provide a radiographic means of distinguishing chordoma from other spinal lesions.

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