HOXD12 and oligodendroglioma: For our analysis, we included EORTC patients who met the following three criteria: (1) their tumor met the current WHO CNS classification system definition of oligodendroglioma (including 1p/19q-codeletion), (2) they were treated with the trial’s uniform chemoradiation regimen (RT + PCV), and (3) their tumor had methylation data sufficient to determine HOXD12 gene body methylation status.