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Early identification of brain cancer with perfusion MRI

Perfusion MRI has been reported to be able to detect changes in brain blood volume that often precede the cancerous transformation of brain tumors. “Patients with low-grade gliomas are often young and may remain clinically well for many years but, at an unpredictable time their tumor will transform to an aggressively high-grade glioma,” said Andrew Waldman, the study’s coauthor, “We found that increases in blood volume within the tumor measured noninvasively by perfusion MRI precede other markers of malignant transformation by a year or more.” Low-grade gliomas are benign brain tumors that grow slowly over a long period of time but eventually progress to high-grade gliomas, which are malignant, much more aggressive and have a poor prognosis. Brain tumors can invoke the formation of new blood vessels in a process known as angiogenesis; these abnormal blood vessels lead to increased blood flow and volume. Perfusion MRI is a technique for evaluation of microscopic blood flow in capillaries and venules. A total of 13 patients (seven men and six women; aged 29–69 years) with biopsy-proven low-grade glioma treated only with anti-epileptic drugs underwent perfusion MRI and contrast-enhanced MRI every 6 months to date or until malignant transformation was diagnosed. Seven patients progressed to high-grade malignant gliomas between 6 and 36 months, while disease remained stable in six patients. In the patients whose disease remained stable, regional cerebral blood volume (rCBV) remained relatively stable, increasing from a mean level of 1.31 to 1.52 over the study period. By contrast, the patients exhibiting tumor transformation showed a continuous increase in rCBV up to the point of transformation, when it became apparent on contrast-enhanced MRI images. The rCBV of the transformers increased significantly from 1.94 at study entry to 3.14 12 months prior to transformation, to 3.65 6 months prior to transformation and to 5.36 at the time transformation was diagnosed. This study shows that significant increases in the rCBV provide an important marker of malignant change in gliomas and reflect the earliest stages of the transformation process. It also show that in transforming low-grade glioma, perfusion MRI can demonstrate significant increases in rCBV up to 12 months before contrast-enhanced MRI can. “We have shown that perfusion MRI provides a noninvasive means of assessing the risk of transformation in individual patients,” Waldman said. “Increasing perfusion can be regarded as an early warning sign of impending malignant transformation that can assist radiologists in identifying those patients most likely to benefit from earlier or more aggressive treatment,” he concluded