Recent developments in the molecular characterization and treatment of oligodendroglial tumors.

Although many patients with oligodendrogliomas (ODs) and oligoastrocytomas (OAs) benefit from a combination of surgery and adjuvant radiotherapy, most patients eventually experience recurrence of their disease. Recent evidence has shown that ODs are more chemosensitive than other gliomas, including astrocytomas or glioblastoma multiforme. These initial findings have prompted further study of chemotherapy in treating ODs and mixed OAs. Advances in molecular genetic analysis have led to improvements in predicting response to chemotherapy and prognosis for ODs, OAs, and astrocytomas. Pure ODs are more chemosensitive than mixed ODs. This difference is related to different proportions of 1p/19q loss of heterozygosity in these neoplasms. Therefore, genetic analysis is likely to be key in determining appropriate treatment. The most common first-line chemotherapy for patients with OD is a procarbazine, lomustine, and vincristine (PCV) combination regimen. However, this regimen is associated with cumulative myelosuppression, nausea, vomiting, and weight loss. Therefore, other chemotherapy agents and regimens have been investigated. Perhaps the most promising is temozolomide, a novel alkylating agent that freely crosses the blood-brain barrier. Temozolomide is approved in the United States for the treatment of recurrent anaplastic astrocytomas and in Europe for any recurrent high-grade gliomas. Initial reports suggest that temozolomide is effective in treating ODs as first- and second-line chemotherapy. Unlike the PCV regimen, temozolomide is not associated with cumulative myelosuppression and is usually well tolerated. Further studies are needed to confirm the efficacy and safety profile of temozolomide and to determine the optimal dose and schedule for treating ODs.