LGG-15. COMPREHENSIVE ANALYSIS OF MYB/MYB1-ALTERED GLIOMAS: A MULTI-INSTITUTIONAL EXPERIENCE OF 33 GLIOMAS

BACKGROUND: Pediatric diffuse gliomas harbor recurrent genetic alterations, including those in MYB and MYBL1. Regardless of histopathologic classification, low-grade diffuse gliomas with MYB/MYBL1 alterations represent a single disease entity. Additional insight is needed to define optimal therapeutic strategies for these tumors. METHODS: We retrospectively reviewed gliomas with MYB or MYB1L alterations treated or referred for pathologic review at St. Jude Children’s Research Hospital (St. Jude). Tumor specimens were centrally reviewed. Molecular characterization and clinical data were collated from St. Jude and referring institutions. RESULTS: Thirty-three patients were identified. Two tumors had MYBL1 alterations, while 31 had MYB alterations. MYB-QKI fusion was the most common alteration. Eighteen (55%) were male. The median age at diagnosis was 5 years (range, 0–40 years). Most tumors were in the cerebral cortex (22/33), and the most common presentation was seizures (16/33). Three patients (9%) presented with hydrocephalus and required cerebrospinal fluid diversion. Two patients (6%) presented with metastatic disease. Gross-total resection was achieved in 15 patients (45%). Of the 7 patients receiving cytotoxic chemotherapy, no substantial response was observed. Of the 6 patients who received RT, one had disease progression. The median follow-up was 5.9 years. The 5-year event-free survival was 88.1%, while the 5-year overall survival was 96.3%. Two patients died, one of unclear cause and one of treatment-related acute myelogenous leukemia. Using log-rank tests, no difference in outcomes was observed based on molecular characteristics, degree of resection, metastatic status, or treatment modality. CONCLUSIONS: Although tumors with MYB and MYBL1 alterations present with varying molecular and clinical features, they represent a group of tumors with favorable outcomes. Further characterization is required to identify the subgroup of tumors with a higher propensity for progression.