The present study shows that oligodendrogliomas with classic histological features remain a molecularly heterogeneous entity and should be stratified according to 1p/19q status because of its major prognostic relevance. Moreover, 1p/19q codeleted AOs are also heterogeneous. Interestingly, mitotic index, MVP, and necrosis help to classify them into 3 groups associated with distinct genomic alterations.
Objectives: We aimed to study the potential clinical relevance of 9p allelic loss, with or without copy number variation, in 1p/19q codeleted anaplastic oligodendroglial tumors (AOTs).Methods: This study enrolled 216 patients with 1p/19q codeleted AOT. The prognostic value of 9p allelic loss was investigated using a French nation-wide prospective registry, POLA (prise en charge des tumeurs oligodendrogliales anaplasiques) and high-density single nucleotide polymorphism arrays. We validated our results using the Repository of Molecular Brain Neoplasia Data (REMBRANDT) dataset.
Results:The minimal common region of allelic loss in chromosome arm 9p was 9p21.3. Allelic loss of 9p21.3, detected in 41.7% of tumors, was associated with shorter progression-free and overall survival rates in univariate (p 5 0.008 and p , 0.001, respectively) and multivariate analyses (p 5 0.009 and p 5 0.009, respectively). This finding was validated in the REMBRANDT dataset in univariate and multivariate analysis (p 5 0.01 and p 5 0.01, respectively). 4,5 However, in both studies, the median overall survival (OS) in the 1p/19q codeleted subgroup had a broad range of 95% confidence interval (from 6.4 to more than 12 years in one study and a 5-year OS rate from 60.3% to 86.4% in the other study), 4,5 suggesting that some patients would have a less favorable prognosis. Identification of novel biomarkers in this tumor subgroup would help to better stratify patients with 1p/19q codeleted AOT.
Conclusion:Although promising novel somatic mutations in CIC (capicua transcriptional repressor) and FUBP1 (far upstream element binding protein 1) have been identified in 1p/19q codeleted
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