CT Perfusion in the Prognostication of Cerebral High Grade Glioma

Purpose of the research: Evaluate the utility of the non-invasive imaging tool of computed tomography (CT) perfusion in preoperative prognostication of high grade cerebral gliomas.

Background information: Brain tumour affects approximately 2300 individuals per year in Canada. High grade glioma is the most common primary brain tumour in adults and accounts for approximately 2.5% of all cancer deaths. The real incidence of high grade glioma in the country is not known, but it affects approximately 2 per 100,000 people per year in Nova Scotia. Non-invasive, accurate and timely diagnosis is imperative.

High grade glioma is an aggressive neoplasm, and the median survival of affected patients is 12 months, irrespective of any form of treatment. The prognosis of these patients can only be determined on pathology after biopsy or surgery. Conventional imaging techniques such as as magnetic resonance imaging(MRI) alone do not help in predicting the level of malignancy of cerebral gliomas. Formation of new blood vessels plays a central role in the growth and spread of tumours. The advanced imaging tool of computed tomography(CT) perfusion can be used to study blood supply to the tumor at the level of capillaries. This information permits determination of aggressiveness of cerebral gliomas at the time of diagnosis.

To direct better and aggressive care in patients with high grade cerebral glioma, it is important to identify patients whose life expectancy could be relatively longer. The two high grades of gliomas have been grouped together in the literature for both treatment and prognosis. There are only a few studies that have addressed the differentiation of the two higher grades of gliomas. Some of these are our own preliminary studies. In a preliminary study of 20 such patients,investigators have shown that CT perfusion can predict survival, irrespective of the pathological grade and treatement received. In the present study, investigators would like to extend our preliminary findings in a larger group of patients to ensure that this technique is indeed robust. In patients with shorter survival, the perfusion parameters may help in identifying new therapeutic targets (e.g., anti-angiogenic agents) that may help in the treatment of these patients.

Both CT and MR perfusion studies can be used to assess the blood supply of brain tumors. MR perfusion is limited in terms of absolute quantification of the perfusion parameters due to the non-linear relationship between the concentration of contrast material and the signal intensity change. MR perfusion studies also require two bolus injections of contrast agents. CT perfusion is a widely available and reliable technique which can give absolute quantification of perfusion parameters with a single acquisition and single bolus of a contrast agent.