Vascular endothelial growth factor expression in oligodendrogliomas: a correlative study with Sainte-Anne malignancy grade, growth fraction and patient survival

Microangiogenesis is a delayed but crucial event in the malignant progressi on of oligodendrogliomas. Accordingly, in the new Sainte-Anne grading syste m of oligodendrogliomas, endothelial hyperplasia and contrast enhancement, both being indicators of microangiogenesis, are key criteria for the distin ction of grade A from grade B tumours. Vascular endothelial growth factor ( VEGF) is a potent angiogenic factor: a strong correlation between VEGF expr ession, Sainte-Anne malignancy grade and patient outcome might thus be expe cted. In order to assess this hypothesis, VEGF immunostaining was performed in a series of 34 oligodendrogliomas that included 11 grade B and 23 grade A, of which nine became grade B during the study period (mean clinical and imaging follow-up: 41 months). VEGF expression correlated strongly with Sa inte-Anne tumour grade (P<0.001), and inversely with patient survival (P<0. 001) and recurrence-free survival (P=0.002). One hundred per cent of grade B but only 17% of grade A were VEGF-positive. By contrast, the MIB-1 labell ing index did not correlate with VEGF expression, total survival or recurre nce-free survival. In accordance with the grading system, this study showed that, in oligodendrogliomas. VEGF expression and microangiogenesis are pro gression-related phenomena that confer on these tumours a growth advantage by presumably reducing hypoxia-induced apoptotic cell death. These findings might have important implications in the future for the indication and tim ing of anti-angiogenic therapies.