P20.06.b systemic chemotherapy in adult patients with diffuse midline glioma h3k27-altered

Abstract BACKGROUND Adult Diffuse midline glioma (DMG) is a very rare disease. DMGs are currently treated with radiotherapy and temozolomide even if only a few retrospective studies assessed the impact on survival of these approaches. MATERIAL AND METHODS We carried out a multicentric retrospective study of adult patients with DMG to assess the effective role of concurrent and adjuvant chemotherapy. All patients had a diagnosis of DMG - H3K27 altered. Results Overall we included 27 DMG H3K27 mutated patients with a median age of 40 years (range 20-66). Thalamus was the most frequent location (n =10, 37%). Overall, 16 patients (59.3%) underwent biopsy, 9 partial resections (33.3%), and 2 (7.4%) complete resections. The molecular assessment revealed TP53 as the most frequently altered gene (n = 4, 14.8%) followed by PIK3R (n = 2, 7.4%) and NF1 (n = 2, 7.4%). MGMT was methylated in 4 patients (14.8%). After surgery, 22 patients (81.5%) received postoperative radiation therapy (RT). Moreover, 12 patients received concurrent temozolomide (44.4%) and 11 (40.7%) adjuvant temozolomide. Patients receiving adjuvant temozolomide had a significantly longer overall survival (25.3 vs 10.5 months, HR 0.16, 95% CI 0.1 - 0.8, p= 0.02). Adjuvant temozolomide was confirmed to be associated with improved survival also when adjusted for age, surgery received, or tumor location. Conclusion In this multicentric retrospective study, the treatment with adjuvant temozolomide seems to prolong survival in DMG H3K27 altered patients. Further studies are needed to improve survival in these patients.