Early postoperative treatment versus initial observation in CNS WHO grade 2 and 3 oligodendroglioma: clinical outcomes and DNA methylation patterns

In the past decades, ample evidence has shown that combined radio-chemotherapy is superior to either radiotherapy or chemotherapy alone in oligodendroglioma. However, the survival benefit comes at the cost of immediate and long-term toxicities. Therefore, deferring postoperative therapy until progression may be a valid option to delay treatment-related side effects. Still, systematic data and reliable predictive biomarkers are limited. In this large retrospective series of oligodendroglioma cases, we could show that early postoperative treatment is not associated with improved PFS and OS while correcting for baseline differences between both groups. In addition, we performed whole-genome DNA methylation analyses and observed a predictive role of certain methylation patterns independent from MGMT promoter methylation status, extent of resection and CNS WHO grade. The results of this real-life study may serve as a benchmark for future trial planning in oligodendroglioma, and further studies should evaluate the predictive value of DNA methylation profiles. Compare DNA methylation pattern between patients who received adjuvant treatment. Patients were stratified into PFS above (Benefit) or below (No_benefit) the median of all patients receiving early postoperative treatment.