Purpose: To use multimodal magnetic resonance imaging (MRI) to quantify treatment-induced changes in the whole volume of diffuse infiltrating pontine gliomas and correlate them with progression-free survival (PFS).
Methods and materials: This prospective study included 22 children aged 3.3 to 14.7 years (median, 5.9 years). Multimodal MRI was performed at 3 distinct time points: before treatment, the first week following radiation therapy (RT), and 2 months after RT. The imaging protocol included morphologic, multi b-value diffusion; arterial spin labeling; and dynamic susceptibility contrast-enhanced perfusion. Morphologic and multimodal data-lesion volume, diffusion coefficients, relative cerebral blood flow, and relative cerebral blood volume (rCBV)-were recorded at the 3 aforementioned time points. The Wilcoxon test was used to compare each individual parameter variation between time points, and its correlation with PFS was assessed by the Spearman test.
Results: Following RT, the tumors' solid component volume decreased by 40% (P<.001). Their median diffusion coefficients decreased by 20% to 40% (P<.001), while median relative cerebral blood flow increased by 60% to 80% (P<.001) and median rCBV increased by 70% (P<.001). PFS was positively correlated with rCBV measured immediately after RT (P=.003), and in patients whose rCBV was above the cutoff value of 2.46, the median PFS was 4.6 months longer (P=.001). These indexes tended to return to baseline 2 months after RT. Lesion volume before or after RT was not correlated with survival.
Conclusions: Multimodal MRI provides useful information about diffuse infiltrating pontine gliomas' response to treatment; rCBV increases following RT, and higher values are correlated with better PFS. High rCBV values following RT should not be mistaken for progression and could be an indicator of response to therapy.
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