Recurrence of glioblastoma is associated with elevated microvascular transit time heterogeneity and increased hypoxia

Dynamic susceptibility contrast (DSC) perfusion MRI provide information about differences in macro-and microvasculature when executed with gradient-echo (GE; sensitive to macrovasculature) and spin-echo (SE; sensitive to microvasculature) contrast. This study investigated whether there are differences between macro- and microvascular transit time heterogeneity (MVTH and mu VTH) and tissue oxygen tension (PO2(mit)) in newly-diagnosed and recurrent glioblastoma. Fifty-seven patients with glioblastoma (25 newly-diagnosed/32 recurrent) were examined with GE-and SE-DSC perfusion sequences, and a quantitative blood-oxygen-level-dependent (qBOLD) approach. Maps of MVTH, mVTH and coefficient of variation (MCOV and mCOV) were calculated from GE-and SE- DSC data, respectively, using an extended flow-diffusion equation. PO(2)mit maps were calculated from qBOLD data. Newly-diagnosed and recurrent glioblastoma showed significantly lower (P <= 0.001) mCOV values compared to both normal brain and macrovasculature (MCOV) of the lesions. Recurrent glioblastoma had significantly higher mVTH (P = 0.014) and mCOV (P = 0.039) as well as significantly lower PO2(mit) values (P = 0.008) compared to newly-diagnosed glioblastoma. The macrovasculature, however, showed no significant differences. Our findings provide evidence of microvascular adaption in the disorganized tumor vasculature for retaining the metabolic demands in stress response of therapeutically-uncontrolled glioblastomas. Thus, mVTH and PO2(mit) mapping gives insight into the tumor microenvironment (vascular and hypoxic niches) responsible for therapy resistance.