Prognostic factors for low-grade gliomas.

Low-grade gliomas are a heterogenous group of diseases characterized by relatively slow-growing primary brain tumors of astrocytic and/or oligodendroglial origin. Many patients present with easily controlled seizures and remain stable for years, whereas others progress rapidly to higher-grade tumors. Several studies have retrospectively investigated tumor-, patient-, and treatment-related prognostic factors in this patient population. Tumor histology, grade, location, contrast enhancement, and molecular markers have been identified as prognostic factors for survival. Likewise, patient age, performance status, and seizure history are patient-dependent prognostic factors. However, although patients who undergo surgical resection and receive adjuvant radiotherapy tend to have improved survival, treatment-dependent prognostic factors have yet to be definitively identified. Recursive partitioning and multivariant analyses have identified a class of patients with good prognosis. Younger patients with good performance status, non-contrast-enhancing tumors (<5 cm), and tumors of oligodendroglial or mixed-oligoastrocytic subtype have improved survival. The European Organisation for Research and Treatment of Cancer has recently developed a prognostic score based on identified prognostic factors to assist in the management of low-grade gliomas. For patients with a favorable (low-risk) score, treatment with radiotherapy or chemotherapy treatment should be withheld until tumor progression. For patients with a high-risk score, treatment at diagnosis may be indicated. However, other than surgery, the optimal types and sequence of therapies are not yet established. Improvements in defining prognostic factors will assist in low-grade glioma management.