One-third of all primary brain tumors are astrocytomas, the most common type of glioma. Grade
4 astrocytomas, more commonly known as glioblastomas (GBMs), represent about 50% of all
gliomas (annual incidence of over 3 per 100,000) and are associated with high mortality rates
and median patient survival of just 12-15 months post-diagnosis. Treatment response is
assessed by measuring post-treatment tumor size on contrast-enhanced magnetic resonance
images (MRI). However, radiation and chemotherapy cause inflammatory and necrotic changes
which, like actual tumor progression itself, demonstrate contrast enhancement on the first
post-treatment MRI scan. This enhancement eventually subsides (typically within 6 months of
treatment) and is known as pseudoprogression (PsP). Currently, there is no gold standard
noninvasive tool for distinguishing between pseudoprogression and progressive disease.
Dynamic susceptibility-weighted contrast-enhanced perfusion MRI (DSC perfusion MRI) permits
measurement of hemodynamic imaging variables. Previous literature reports attempted to use
some or all of these metrics to assess their utility in distinguishing PsP from true cancer
progression. These studies showed mixed results, likely due to a number of factors, including
poor statistical power, poorly defined PsP, analysis of multiple cancer grades and types, and
varied analysis methodologies. The investigators aim to address these issues in this study.