Clinical and Genomic Characteristics of Adult Diffuse Midline Glioma

PURPOSE: The treatment outcomes and genomic profiles of diffuse midline glioma (DMG) in adult patients are rarely characterized. We performed a retrospective study to evaluate the clinicogenomic profiles of adult patients with brain DMG. MATERIALS AND METHODS: Patients aged ≥ 18 years diagnosed with brain DMG at Seoul National University Hospital were included. The clinicopathological parameters, treatment outcomes, survival, and genomic profiles using 82-gene targeted next-generation sequencing (NGS) were analyzed. The 6-month progression-free survival (PFS6) after radiotherapy and overall survival (OS) were evaluated. RESULTS: Thirty-three patients with H3-mutant brain DMG were identified. The median OS from diagnosis was 21.8 months (95% confidence interval [CI], 13.2 to not available [NA]) and involvement of the ponto-medullary area tended to have poor OS (median OS, 20.4 months [95% CI, 9.3 to NA] vs. 43.6 months [95% CI, 18.2 to NA]; p=0.07). Twenty-four patients (72.7%) received radiotherapy with or without temozolomide. The PFS6 rate was 83.3% (n=20). Patients without progression at 6 months showed significantly prolonged OS compared with those with progression at 6 months (median OS, 24.9 months [95% CI, 20.4 to NA] vs. 10.8 months [95% CI, 4.0 to NA]; p=0.02, respectively). Targeted NGS was performed in 13 patients with DMG, among whom nine (69.2%) harbored concurrent TP53 mutation. Two patients (DMG14 and DMG23) with PIK3CA(R38S+E545K) and KRAS(G12A) mutations received matched therapies. Patient DMG14 received sirolimus with a PFS of 8.4 months. CONCLUSION: PFS6 after radiotherapy was associated with prolonged survival in adult patients with DMG. Genome-based matched therapy may be an encouraging approach for progressive adult patients with DMG.