In Search of Prognostic Factors in Grade 2 Gliomas

Grade 2 gliomas are malignant brain tumours affecting otherwise healthy adults. Although the long-term prognosis is poor, many patients are well and may have a high quality of life for several years. There is, however, a large variability in the natural course of the disease which makes it essential to identify patients who might benefit from early surgery or radio-therapy. The aim of the present thesis was to define new and clinically useful prognostic markers that may assist in the initial treatment decision and in patient follow-up. A retrospective study of 189 patients with gliomas WHO grade 2 showed no advantage in survival of early tumour resection or radiotherapy, and confirmed that histological subtype and patient age are the most important predictors of survival (I). In 89 patients, the pre-treatment uptake of 11C-methionine (MET) measured with positron emission tomography (PET) was identified as a prognostic marker for survival (II). At the time of tumour progression, irradiated tumours demonstrated signs of a residual radiotherapeutic effect that correlated with the pre-treatment uptake of MET (III). Pre-treatment uptake of MET may, therefore, be important both in predicting the natural course of the disease and the response after treatment. Immunohistochemical staining of 40 tumour samples showed an inverse association between the number of tumour cells expressing platelet-derived growth factor alpha receptor (PDGFRa) and survival (IV). Also, a reduction was observed in the number of receptor-positive cells after malignant transformation, supporting the prognostic value of PDGFRa. Lumbar puncture was performed in eight patients with newly diagnosed low-grade gliomas to identify three important growth factors in tumour development. Neither PDGF nor vascular endothelial growth factor (VEGF) were detected in the cerebrospinal fluid (CSF), and fibroblast growth factor 2 (FGF-2) was measurable at extremely low concentrations in two of the patients (V). A proteome screening of the CSF, using two-dimensional gel electrophoresis and mass spectrometry, detected alpha 2-HS glycoprotein at significantly higher concentrations than in a control group (VI). This glycoprotein emerges as a novel substance in glioma research and may be of great interest because of its suggested involvement in the embryonic development of the neocortex