Object: Demonstration of the loss of chromosomes 1p and 19q in the presence of a brain neoplasm marks the emergence of genotype as a prognostic indicator. The authors report gene expression data for oligodendroglioma and correlate genotype with response to therapy. Gene expression subgroups may represent distinct types of disease.
Methods: Eighty-seven cases of supratentorial oligodendroglioma were selected from 145 cases treated in a single center between January 1990 and December 2001. Fluorescence in situ hybridization was used to determine the status of chromosomes 1p and 19q. Parameters evaluated included clinical data and radiological and histological features. Univariate and multivariate analyses were performed and a probability value less than 0.05 was considered significant. The patients included 48 women and 39 men. The overall mean age at presentation was 45 years for women and 36 years for men (p = 0.006). The univariate analysis identified the following as favorable prognostic factors: younger patient age (p = 10(-5)), female sex (p = 0.0025), seizure as a presenting symptom (p = 10(-5)), normal clinical examination (p = 10(-5)), absence of lesion enhancement on neuroimaging studies (p = 0.0231), lack of histological necrosis (p = 0.0003), absence of mitoses (p = 0.0014), 1p and 19q deletions (p = 0.0001), absence of recurrence (p = 0.0021), and adjuvant radiotherapy and/or chemotherapy (p = 10(-5)). The multivariate analysis identified patient age (p = 10(-5)) and chromosomal anomalies (p = 0.002) as independently linked to survival. Three molecular subtypes emerged: oligodendroglioma with 1p and 19q deletions, oligodendroglioma demonstrating polysomia and a lack of meaningful response to radiotherapy or chemotherapy, and oligodendroglioma with no 1p-9q deletion in which partial response was seen.
Conclusions: According to our data, oligodendrogliomas could be divided into three molecular subtypes. Although chemotherapy seems efficient for managing this tumor, additional studies should be conducted to compare the efficacy of radiotherapy and chemotherapy.