Prognostic significance of clinical and angiogenesis-related factors in low-grade oligodendrogliomas

Abstract

BACKGROUND Keeping in mind that oligodendrogliomas have unpredictable biological behavior, the aim of this study is to investigate the prognostic significance of VEGF expression and microvessel density in a homogenous series of low-grade oligodendrogliomas. METHODS For this study 36 patients with a low-grade oligodendroglioma treated by surgical resection and radiotherapy were selected. At the time of surgery, in all cases the Karnofsky Performance Scale (KPS) score was more than 70, and the study of the resected tumor disclosed a Ki-67/MIB-1 labeling index (MBI-1 LI) less than 1%. In this homogenous series, immunohistochemical studies were performed using monoclonal antibodies against VEGF in order to study the expression of this cytokine, and against vascular endothelial CD-34 antigen, in order to identify microvessels. RESULTS Our results show that in contrast to low-grade astrocytomas, low-grade oligodendrogliomas lacked immunoreactive VEGF. Oligodendrogliomas with low vascular density (less than 20 microvessels per microscopical field, at 200 ×) or high vascular density (more than 100 microvessels per field, at 200 ×) were identified, but this factor had no influence on the survival rate of patients. On the other hand, analysis of the present series showed that clinical factors, such as age or extent of surgical resection, were not significantly associated with survival. CONCLUSIONS In contrast to low-grade astrocytomas, the angiogenesis score of low-grade oligodendrogliomas (counting the number of microvessels in tumor tissue) adds little information to help predict tumor behavior.