Guidelines for the treatment of oligodendroglioma: an evidence-based medicine approach.

The sensitivity to chemotherapy of oligodendroglioma (OD) is the major clinical distinction between oligodendroglial and astrocytic tumours. In particular, chemotherapy with alkylating agents (PCV chemotherapy, temozolomide) in recurrent OD is of proven efficacy, with 50 to 70% of patients responding. The value of adjuvant chemotherapy in newly diagnosed tumours still remains to be proven. The efficacy of radiotherapy (RT) has never been proven in a phase III trial on OD, but based on historical phase III trials on anaplastic glioma this generally considered part of standard treatment of these tumours. Recent molecular biological studies show that OD are characterised by a combined loss of the short arm of chromosome 1 (1p) and the long arm of chromosome 19 (19 q). This combined loss of 1p and 19 q also identifies a group of tumours with a better response to chemotherapy and a longer survival after RT. It is expected that this knowledge will change the diagnostic criteria for OD and will help to select patients for specific treatments. However, improvement of the currently available treatments is needed, as the outcome of these patients remains dismal.