Low-grade gliomas are primary brain tumors that grow slowly over several years. Eventually, almost all low-grade gliomas progress to high-grade gliomas, which carry a poor prognosis. For the study, the researchers performed perfusion MRI on 13 patients with low-grade gliomas to determine whether relative cerebral blood volume (rCBV) changes are an indicator of future malignant transformation.
Brain tumors can bring about the formation of new blood vessels, a process known as angiogenesis. These vessels are abnormal and lead to changes in blood volume and flow. Using perfusion MRI, radiologists can detect these changes well before they become apparent on contrast-enhanced MR images.
The patients underwent perfusion MRI and contrast-enhanced MRI every six months for up to three years. Seven patients progressed to high-grade, malignant gliomas between six and 36 months. In the six patients whose disease remained stable, rCBV remained relatively stable, increasing from a mean level of 1.31 at the beginning of the study to 1.52 over the follow-up period.
However, in the patients exhibiting tumor transformation, mean rCBV increased progressively from 1.94 at study entry to 3.14 twelve months prior to transformation, to 3.65 six months prior to transformation and to 5.36 at the time transformation was diagnosed.
These findings suggest that significant changes in rCBV represent an important marker of malignant change in gliomas and reflect the earliest stages of the transformation process. Further, the data support the likelihood that the cellular processes underlying malignant transformation may occur twelve months or more before visible on contrast MRI.
MEDICA.de; Source: Radiological Society of North America