Despite accumulating knowledge regarding molecular backgrounds, the optimal management strategy for low-grade
gliomas remains controversial. One reason is the marked heterogeneity in the
clinical course. To establish an accurate subclassification of low-grade
gliomas, we retrospectively evaluated
isocitrate dehydrogenase-1 (IDH1) mutation in clinical specimens of diffuse
astrocytomas (DA) and oligodendroglial
tumors separately. No patients were treated with early
radiotherapy, and modified PCV
chemotherapy was used for postoperative
residual tumors or recurrence in oligodendroglial
tumors. Immunohistochemical evaluation of IDH status, p53 status,
O(6)-methylguanine methyltransferase expression, and the MIB-1 index were performed. The 1p and 19q status was analyzed with fluorescence in situ hybridization. Ninety-four patients were followed for a median period of 8.5 years. For
DAs, p53 was prognostic for progression- free survival (PFS) and IDH1 was significant for overall survival (OS) with multivariate analysis. In contrast, for oligodendroglial
tumors, none of the parameters was significant for PFS or OS. Thus, the significance of IDH1 mutation is not clear in oligodendroglial
tumors that are homogeneously indolent and chemosensitive. In contrast,
DAs are heterogeneous
tumors including some potentially malignant
tumors that can be predicted by examining the IDH1 mutation status.