JS07.5.A PROGNOSTIC FACTORS ASSOCIATED WITH POOR OUTCOME IN ADULT PATIENTS WITH MEDULLOBLASTOMA

Abstract BACKGROUND Medulloblastoma (MB) is a rare tumor in adults. Current recommendations are based on scarce data available in adults, and mostly derived from pediatric series. Prognostic factors have not been uniformly defined in adults to date. MATERIAL AND METHODS We retrospectively collected all cases of adult patients diagnosed and treated between 1995 and 2019 in our institution for histopathological proven MB. We described patient´s characteristics, disease features, treatment modalities and studied the prognostic factors for survival outcomes using univariate and multivariate analysis. RESULTS We identified a total of 89 cases. Male gender (66%), lateral cerebellar location (48%), desmoplastic/nodular histology (43%), Sonic Hedgehog molecular group (76%) and Chang´s M0 (72%) were the most frequent patient´s and disease characteristics. Patients mostly achieved complete resection/near total resection (62%); surgery followed by chemotherapy/radiotherapy (CT/RT) was the most frequent initial strategy (76%), favoring carboplatin-based regimens (70%), posterior fossa RT ≥50 Gy (71%) and craniospinal RT ≥ 30 Gy (59%) as the most frequently regimen used. According to the Association of French Speaking Neuro-oncologists and the European Reference Network on Rare Adult Cancers risk scales (ANOCEF and EURACAN), we found 44 and 48% of intermediate-risk patients and 49 and 45% of high-risk patients, respectively. Both cerebral and spinal presentation at diagnosis was documented in 16 (18%) patients. Complete response was achieved in 71(80%) patients. Nine was the maximal number of progressions documented, 35(39%) patients relapsed, CT was the preferred strategy at relapses, privileging carboplatin-based regimens at first relapse. The median overall survival (mOS) was 124.42 months (95%CI 68.53 - 180.11) and the median progression free survival (mPFS) was 30.48 months (95%CI 13.46 - 47.51), the 5-year OS was 53% and the 5-year PFS was 51%. In multivariate analysis, Chang´s ≥ M2 metastatic classification (p=0.001), no CT in association to RT (p=0.005), and lower doses on craniospinal RT