RADT-34. ANALYSIS OF A METHYLATION CLASS-GUIDED RADIOTHERAPY IN MENINGIOMA PATIENTS - AND THE PROSPECTIVE PHASE II MARCIE TRIAL WITH CARBON-ION BOOST RADIOTHERAPY

Abstract Meningiomas represent the most common primary brain tumor type, with a recurrence rate of approximately 20% following resection. Classification by molecular classes was demonstrated to be more accurate in identifying patients at high risk disease progression meningiomas, compared WHO grading only. Novel radiotherapeutic modalities using protons or carbon ions provide an increased relative biological effectiveness (RBE) photons, enabling higher local dose deposition while reducing radiation for organs risks. The prospective single-arm phase II - MARCIE trial investigated bimodal radiotherapy photons (50 Gy 25 fractions) and carbon-ions boost 18 6 fractions. Local progression-free survival after 3 years defined as endpoint. In total, 33 were recruited before termination trial. After years, free estimated 94.7% overall 89.8%. Serious adverse events form necrosis observed cases, requiring subsequent treatment bevacizumab. Post-hoc DNA methylation profiling revealed that relapses occur frequently high-risk meningiomas radiotherapy, intermediate risk-group, confirming prognostic relevance methylation-based meningioma classifier.Subsequently, retrospective matched-pair analysis performed compare irradiated (n > 100) non-irradiated stratified into groups (ben, int, high). clinical benefit postoperative escalation regard control are currently being assessed respective classes. Postoperative, carbon-ion auspicious modality excellent Molecular stratification is crucial who might from radiotherapy.